cc: Chromify LayerTreeHostCommon

cc/trees/layer_tree_host_common.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/layer_tree_host_common.h"
 
 #include <algorithm>
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/layers/heads_up_display_layer_impl.h"
 #include "cc/layers/layer.h"
 #include "cc/layers/layer_impl.h"
 #include "cc/layers/layer_iterator.h"
 #include "cc/layers/render_surface.h"
 #include "cc/layers/render_surface_impl.h"
 #include "cc/trees/layer_sorter.h"
 #include "cc/trees/layer_tree_impl.h"
 #include "ui/gfx/point_conversions.h"
 #include "ui/gfx/rect_conversions.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
-ScrollAndScaleSet::ScrollAndScaleSet()
-{
-}
-
-ScrollAndScaleSet::~ScrollAndScaleSet()
-{
-}
-
-static void sortLayers(std::vector<scoped_refptr<Layer> >::iterator forst, std::vector<scoped_refptr<Layer> >::iterator end, void* layerSorter)
-{
-    NOTREACHED();
-}
-
-static void sortLayers(std::vector<LayerImpl*>::iterator first, std::vector<LayerImpl*>::iterator end, LayerSorter* layerSorter)
-{
-    DCHECK(layerSorter);
-    TRACE_EVENT0("cc", "layer_tree_host_common::sortLayers");
-    layerSorter->Sort(first, end);
-}
-
-inline gfx::Rect calculateVisibleRectWithCachedLayerRect(const gfx::Rect& targetSurfaceRect, const gfx::Rect& layerBoundRect, const gfx::Rect& layerRectInTargetSpace, const gfx::Transform& transform)
-{
-    // Is this layer fully contained within the target surface?
-    if (targetSurfaceRect.Contains(layerRectInTargetSpace))
-        return layerBoundRect;
-
-    // If the layer doesn't fill up the entire surface, then find the part of
-    // the surface rect where the layer could be visible. This avoids trying to
-    // project surface rect points that are behind the projection point.
-    gfx::Rect minimalSurfaceRect = targetSurfaceRect;
-    minimalSurfaceRect.Intersect(layerRectInTargetSpace);
-
-    // Project the corners of the target surface rect into the layer space.
-    // This bounding rectangle may be larger than it needs to be (being
-    // axis-aligned), but is a reasonable filter on the space to consider.
-    // Non-invertible transforms will create an empty rect here.
-
-    gfx::Transform surfaceToLayer(gfx::Transform::kSkipInitialization);
-    if (!transform.GetInverse(&surfaceToLayer)) {
-        // TODO(shawnsingh): Either we need to handle uninvertible transforms
-        // here, or DCHECK that the transform is invertible.
-    }
-    gfx::Rect layerRect = gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(surfaceToLayer, gfx::RectF(minimalSurfaceRect)));
-    layerRect.Intersect(layerBoundRect);
-    return layerRect;
-}
-
-gfx::Rect LayerTreeHostCommon::calculateVisibleRect(const gfx::Rect& targetSurfaceRect, const gfx::Rect& layerBoundRect, const gfx::Transform& transform)
-{
-    gfx::Rect layerInSurfaceSpace = MathUtil::MapClippedRect(transform, layerBoundRect);
-    return calculateVisibleRectWithCachedLayerRect(targetSurfaceRect, layerBoundRect, layerInSurfaceSpace, transform);
+ScrollAndScaleSet::ScrollAndScaleSet() {}
+
+ScrollAndScaleSet::~ScrollAndScaleSet() {}
+
+static void SortLayers(std::vector<scoped_refptr<Layer> >::iterator forst,
+                       std::vector<scoped_refptr<Layer> >::iterator end,
+                       void* layer_sorter) {
+  NOTREACHED();
+}
+
+static void SortLayers(std::vector<LayerImpl*>::iterator first,
+                       std::vector<LayerImpl*>::iterator end,
+                       LayerSorter* layer_sorter) {
+  DCHECK(layer_sorter);
+  TRACE_EVENT0("cc", "LayerTreeHostCommon::SortLayers");
+  layer_sorter->Sort(first, end);
+}
+
+inline gfx::Rect CalculateVisibleRectWithCachedLayerRect(
+    gfx::Rect target_surface_rect,
+    gfx::Rect layer_bound_rect,
+    gfx::Rect layer_rect_in_target_space,
+    const gfx::Transform& transform) {
+  // Is this layer fully contained within the target surface?
+  if (target_surface_rect.Contains(layer_rect_in_target_space))
+    return layer_bound_rect;
+
+  // If the layer doesn't fill up the entire surface, then find the part of
+  // the surface rect where the layer could be visible. This avoids trying to
+  // project surface rect points that are behind the projection point.
+  gfx::Rect minimal_surface_rect = target_surface_rect;
+  minimal_surface_rect.Intersect(layer_rect_in_target_space);
+
+  // Project the corners of the target surface rect into the layer space.
+  // This bounding rectangle may be larger than it needs to be (being
+  // axis-aligned), but is a reasonable filter on the space to consider.
+  // Non-invertible transforms will create an empty rect here.
+
+  gfx::Transform surface_to_layer(gfx::Transform::kSkipInitialization);
+  if (!transform.GetInverse(&surface_to_layer)) {
+    // TODO(shawnsingh): Either we need to handle uninvertible transforms
+    // here, or DCHECK that the transform is invertible.
+  }
+  gfx::Rect layer_rect = gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
+      surface_to_layer, gfx::RectF(minimal_surface_rect)));
+  layer_rect.Intersect(layer_bound_rect);
+  return layer_rect;
+}
+
+gfx::Rect LayerTreeHostCommon::CalculateVisibleRect(
+    gfx::Rect target_surface_rect,
+    gfx::Rect layer_bound_rect,
+    const gfx::Transform& transform) {
+  gfx::Rect layer_in_surface_space =
+      MathUtil::MapClippedRect(transform, layer_bound_rect);
+  return CalculateVisibleRectWithCachedLayerRect(
+      target_surface_rect, layer_bound_rect, layer_in_surface_space, transform);
+}
+
+template <typename LayerType> static inline bool IsRootLayer(LayerType* layer) {
+  return !layer->parent();
 }
 
 template <typename LayerType>
-static inline bool isRootLayer(LayerType* layer)
-{
-    return !layer->parent();
-}
-
-template<typename LayerType>
-static inline bool layerIsInExisting3DRenderingContext(LayerType* layer)
-{
-    // According to current W3C spec on CSS transforms, a layer is part of an established
-    // 3d rendering context if its parent has transform-style of preserves-3d.
-    return layer->parent() && layer->parent()->preserves_3d();
-}
-
-template<typename LayerType>
-static bool isRootLayerOfNewRenderingContext(LayerType* layer)
-{
-    // According to current W3C spec on CSS transforms (Section 6.1), a layer is the
-    // beginning of 3d rendering context if its parent does not have transform-style:
-    // preserve-3d, but this layer itself does.
-    if (layer->parent())
-        return !layer->parent()->preserves_3d() && layer->preserves_3d();
-
-    return layer->preserves_3d();
-}
-
-template<typename LayerType>
-static bool isLayerBackFaceVisible(LayerType* layer)
-{
-    // The current W3C spec on CSS transforms says that backface visibility should be
-    // determined differently depending on whether the layer is in a "3d rendering
-    // context" or not. For Chromium code, we can determine whether we are in a 3d
-    // rendering context by checking if the parent preserves 3d.
-
-    if (layerIsInExisting3DRenderingContext(layer))
-        return layer->draw_transform().IsBackFaceVisible();
-
-    // In this case, either the layer establishes a new 3d rendering context, or is not in
-    // a 3d rendering context at all.
+static inline bool LayerIsInExisting3DRenderingContext(LayerType* layer) {
+  // According to current W3C spec on CSS transforms, a layer is part of an
+  // established 3d rendering context if its parent has transform-style of
+  // preserves-3d.
+  return layer->parent() && layer->parent()->preserves_3d();
+}
+
+template <typename LayerType>
+static bool IsRootLayerOfNewRenderingContext(LayerType* layer) {
+  // According to current W3C spec on CSS transforms (Section 6.1), a layer is
+  // the beginning of 3d rendering context if its parent does not have
+  // transform-style: preserve-3d, but this layer itself does.
+  if (layer->parent())
+    return !layer->parent()->preserves_3d() && layer->preserves_3d();
+
+  return layer->preserves_3d();
+}
+
+template <typename LayerType>
+static bool IsLayerBackFaceVisible(LayerType* layer) {
+  // The current W3C spec on CSS transforms says that backface visibility should
+  // be determined differently depending on whether the layer is in a "3d
+  // rendering context" or not. For Chromium code, we can determine whether we
+  // are in a 3d rendering context by checking if the parent preserves 3d.
+
+  if (LayerIsInExisting3DRenderingContext(layer))
+    return layer->draw_transform().IsBackFaceVisible();
+
+  // In this case, either the layer establishes a new 3d rendering context, or
+  // is not in a 3d rendering context at all.
+  return layer->transform().IsBackFaceVisible();
+}
+
+template <typename LayerType>
+static bool IsSurfaceBackFaceVisible(LayerType* layer,
+                                     const gfx::Transform& draw_transform) {
+  if (LayerIsInExisting3DRenderingContext(layer))
+    return draw_transform.IsBackFaceVisible();
+
+  if (IsRootLayerOfNewRenderingContext(layer))
     return layer->transform().IsBackFaceVisible();
-}
-
-template<typename LayerType>
-static bool isSurfaceBackFaceVisible(LayerType* layer, const gfx::Transform& drawTransform)
-{
-    if (layerIsInExisting3DRenderingContext(layer))
-        return drawTransform.IsBackFaceVisible();
-
-    if (isRootLayerOfNewRenderingContext(layer))
-        return layer->transform().IsBackFaceVisible();
-
-    // If the renderSurface is not part of a new or existing rendering context, then the
-    // layers that contribute to this surface will decide back-face visibility for themselves.
-    return false;
-}
-
-template<typename LayerType>
-static inline bool layerClipsSubtree(LayerType* layer)
-{
-    return layer->masks_to_bounds() || layer->mask_layer();
-}
-
-template<typename LayerType>
-static gfx::Rect calculateVisibleContentRect(LayerType* layer, const gfx::Rect& ancestorClipRectInDescendantSurfaceSpace, const gfx::Rect& layerRectInTargetSpace)
-{
-    DCHECK(layer->render_target());
-
-    // Nothing is visible if the layer bounds are empty.
-    if (!layer->DrawsContent() || layer->content_bounds().IsEmpty() || layer->drawable_content_rect().IsEmpty())
-        return gfx::Rect();
-
-    // Compute visible bounds in target surface space.
-    gfx::Rect visibleRectInTargetSurfaceSpace = layer->drawable_content_rect();
-
-    if (!layer->render_target()->render_surface()->clip_rect().IsEmpty()) {
-        // In this case the target surface does clip layers that contribute to
-        // it. So, we have to convert the current surface's clipRect from its
-        // ancestor surface space to the current (descendant) surface
-        // space. This conversion is done outside this function so that it can
-        // be cached instead of computing it redundantly for every layer.
-        visibleRectInTargetSurfaceSpace.Intersect(ancestorClipRectInDescendantSurfaceSpace);
-    }
-
-    if (visibleRectInTargetSurfaceSpace.IsEmpty())
-        return gfx::Rect();
-
-    return calculateVisibleRectWithCachedLayerRect(visibleRectInTargetSurfaceSpace, gfx::Rect(gfx::Point(), layer->content_bounds()), layerRectInTargetSpace, layer->draw_transform());
-}
-
-static inline bool transformToParentIsKnown(LayerImpl*)
-{
+
+  // If the render_surface is not part of a new or existing rendering context,
+  // then the layers that contribute to this surface will decide back-face
+  // visibility for themselves.
+  return false;
+}
+
+template <typename LayerType>
+static inline bool LayerClipsSubtree(LayerType* layer) {
+  return layer->masks_to_bounds() || layer->mask_layer();
+}
+
+template <typename LayerType>
+static gfx::Rect CalculateVisibleContentRect(
+    LayerType* layer,
+    gfx::Rect ancestor_clip_rect_in_descendant_surface_space,
+    gfx::Rect layer_rect_in_target_space) {
+  DCHECK(layer->render_target());
+
+  // Nothing is visible if the layer bounds are empty.
+  if (!layer->DrawsContent() || layer->content_bounds().IsEmpty() ||
+      layer->drawable_content_rect().IsEmpty())
+    return gfx::Rect();
+
+  // Compute visible bounds in target surface space.
+  gfx::Rect visible_rect_in_target_surface_space =
+      layer->drawable_content_rect();
+
+  if (!layer->render_target()->render_surface()->clip_rect().IsEmpty()) {
+    // In this case the target surface does clip layers that contribute to
+    // it. So, we have to convert the current surface's clipRect from its
+    // ancestor surface space to the current (descendant) surface
+    // space. This conversion is done outside this function so that it can
+    // be cached instead of computing it redundantly for every layer.
+    visible_rect_in_target_surface_space.Intersect(
+        ancestor_clip_rect_in_descendant_surface_space);
+  }
+
+  if (visible_rect_in_target_surface_space.IsEmpty())
+    return gfx::Rect();
+
+  return CalculateVisibleRectWithCachedLayerRect(
+      visible_rect_in_target_surface_space,
+      gfx::Rect(gfx::Point(), layer->content_bounds()),
+      layer_rect_in_target_space,
+      layer->draw_transform());
+}
+
+static inline bool TransformToParentIsKnown(LayerImpl* layer) { return true; }
+
+static inline bool TransformToParentIsKnown(Layer* layer) {
+
+  return !layer->TransformIsAnimating();
+}
+
+static inline bool TransformToScreenIsKnown(LayerImpl* layer) { return true; }
+
+static inline bool TransformToScreenIsKnown(Layer* layer) {
+  return !layer->screen_space_transform_is_animating();
+}
+
+template <typename LayerType>
+static bool LayerShouldBeSkipped(LayerType* layer) {
+  // Layers can be skipped if any of these conditions are met.
+  //   - does not draw content.
+  //   - is transparent
+  //   - has empty bounds
+  //   - the layer is not double-sided, but its back face is visible.
+  //
+  // Some additional conditions need to be computed at a later point after the
+  // recursion is finished.
+  //   - the intersection of render surface content and layer clipRect is empty
+  //   - the visibleContentRect is empty
+  //
+  // Note, if the layer should not have been drawn due to being fully
+  // transparent, we would have skipped the entire subtree and never made it
+  // into this function, so it is safe to omit this check here.
+
+  if (!layer->DrawsContent() || layer->bounds().IsEmpty())
     return true;
-}
-
-static inline bool transformToParentIsKnown(Layer* layer)
-{
-
-    return !layer->TransformIsAnimating();
-}
-
-static inline bool transformToScreenIsKnown(LayerImpl*)
-{
+
+  LayerType* backface_test_layer = layer;
+  if (layer->use_parent_backface_visibility()) {
+    DCHECK(layer->parent());
+    DCHECK(!layer->parent()->use_parent_backface_visibility());
+    backface_test_layer = layer->parent();
+  }
+
+  // The layer should not be drawn if (1) it is not double-sided and (2) the
+  // back of the layer is known to be facing the screen.
+  if (!backface_test_layer->double_sided() &&
+      TransformToScreenIsKnown(backface_test_layer) &&
+      IsLayerBackFaceVisible(backface_test_layer))
     return true;
-}
-
-static inline bool transformToScreenIsKnown(Layer* layer)
-{
-    return !layer->screen_space_transform_is_animating();
-}
-
-template<typename LayerType>
-static bool layerShouldBeSkipped(LayerType* layer)
-{
-    // Layers can be skipped if any of these conditions are met.
-    //   - does not draw content.
-    //   - is transparent
-    //   - has empty bounds
-    //   - the layer is not double-sided, but its back face is visible.
-    //
-    // Some additional conditions need to be computed at a later point after the recursion is finished.
-    //   - the intersection of render surface content and layer clipRect is empty
-    //   - the visibleContentRect is empty
-    //
-    // Note, if the layer should not have been drawn due to being fully transparent,
-    // we would have skipped the entire subtree and never made it into this function,
-    // so it is safe to omit this check here.
-
-    if (!layer->DrawsContent() || layer->bounds().IsEmpty())
-        return true;
-
-    LayerType* backfaceTestLayer = layer;
-    if (layer->use_parent_backface_visibility()) {
-        DCHECK(layer->parent());
-        DCHECK(!layer->parent()->use_parent_backface_visibility());
-        backfaceTestLayer = layer->parent();
-    }
-
-    // The layer should not be drawn if (1) it is not double-sided and (2) the back of the layer is known to be facing the screen.
-    if (!backfaceTestLayer->double_sided() && transformToScreenIsKnown(backfaceTestLayer) && isLayerBackFaceVisible(backfaceTestLayer))
-        return true;
-
-    return false;
-}
-
-static inline bool subtreeShouldBeSkipped(LayerImpl* layer)
-{
-    // The opacity of a layer always applies to its children (either implicitly
-    // via a render surface or explicitly if the parent preserves 3D), so the
-    // entire subtree can be skipped if this layer is fully transparent.
-    return !layer->opacity();
-}
-
-static inline bool subtreeShouldBeSkipped(Layer* layer)
-{
-    // If the opacity is being animated then the opacity on the main thread is unreliable
-    // (since the impl thread may be using a different opacity), so it should not be trusted.
-    // In particular, it should not cause the subtree to be skipped.
-    // Similarly, for layers that might animate opacity using an impl-only
-    // animation, their subtree should also not be skipped.
-    return !layer->opacity() && !layer->OpacityIsAnimating() &&
-           !layer->OpacityCanAnimateOnImplThread();
+
+  return false;
+}
+
+static inline bool SubtreeShouldBeSkipped(LayerImpl* layer) {
+  // The opacity of a layer always applies to its children (either implicitly
+  // via a render surface or explicitly if the parent preserves 3D), so the
+  // entire subtree can be skipped if this layer is fully transparent.
+  return !layer->opacity();
+}
+
+static inline bool SubtreeShouldBeSkipped(Layer* layer) {
+  // If the opacity is being animated then the opacity on the main thread is
+  // unreliable (since the impl thread may be using a different opacity), so it
+  // should not be trusted.
+  // In particular, it should not cause the subtree to be skipped.
+  // Similarly, for layers that might animate opacity using an impl-only
+  // animation, their subtree should also not be skipped.
+  return !layer->opacity() && !layer->OpacityIsAnimating() &&
+         !layer->OpacityCanAnimateOnImplThread();
 }
 
 // Called on each layer that could be drawn after all information from
 // calcDrawProperties has been updated on that layer.  May have some false
 // positives (e.g. layers get this called on them but don't actually get drawn).
-static inline void updateTilePrioritiesForLayer(LayerImpl* layer)
-{
-    layer->UpdateTilePriorities();
-
-    // Mask layers don't get this call, so explicitly update them so they can
-    // kick off tile rasterization.
-    if (layer->mask_layer())
-        layer->mask_layer()->UpdateTilePriorities();
-    if (layer->replica_layer() && layer->replica_layer()->mask_layer())
-      layer->replica_layer()->mask_layer()->UpdateTilePriorities();
-}
-
-static inline void updateTilePrioritiesForLayer(Layer* layer)
-{
-}
-
-template<typename LayerType>
-static bool subtreeShouldRenderToSeparateSurface(LayerType* layer, bool axisAlignedWithRespectToParent)
-{
-    //
-    // A layer and its descendants should render onto a new RenderSurfaceImpl if any of these rules hold:
-    //
-
-    // The root layer should always have a renderSurface.
-    if (isRootLayer(layer))
-        return true;
-
-    // If we force it.
-    if (layer->force_render_surface())
-        return true;
-
-    // If the layer uses a mask.
-    if (layer->mask_layer())
-        return true;
-
-    // If the layer has a reflection.
-    if (layer->replica_layer())
-        return true;
-
-    // If the layer uses a CSS filter.
-    if (!layer->filters().isEmpty() || !layer->background_filters().isEmpty() || layer->filter())
-        return true;
-
-    int numDescendantsThatDrawContent = layer->draw_properties().num_descendants_that_draw_content;
-
-    // If the layer flattens its subtree (i.e. the layer doesn't preserve-3d), but it is
-    // treated as a 3D object by its parent (i.e. parent does preserve-3d).
-    if (layerIsInExisting3DRenderingContext(layer) && !layer->preserves_3d() && numDescendantsThatDrawContent > 0) {
-        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface flattening");
-        return true;
+static inline void UpdateTilePrioritiesForLayer(LayerImpl* layer) {
+  layer->UpdateTilePriorities();
+
+  // Mask layers don't get this call, so explicitly update them so they can
+  // kick off tile rasterization.
+  if (layer->mask_layer())
+    layer->mask_layer()->UpdateTilePriorities();
+  if (layer->replica_layer() && layer->replica_layer()->mask_layer())
+    layer->replica_layer()->mask_layer()->UpdateTilePriorities();
+}
+
+static inline void UpdateTilePrioritiesForLayer(Layer* layer) {}
+
+template <typename LayerType>
+static bool SubtreeShouldRenderToSeparateSurface(
+    LayerType* layer,
+    bool axis_aligned_with_respect_to_parent) {
+  //
+  // A layer and its descendants should render onto a new RenderSurfaceImpl if
+  // any of these rules hold:
+  //
+
+  // The root layer should always have a render_surface.
+  if (IsRootLayer(layer))
+    return true;
+
+  // If we force it.
+  if (layer->force_render_surface())
+    return true;
+
+  // If the layer uses a mask.
+  if (layer->mask_layer())
+    return true;
+
+  // If the layer has a reflection.
+  if (layer->replica_layer())
+    return true;
+
+  // If the layer uses a CSS filter.
+  if (!layer->filters().isEmpty() || !layer->background_filters().isEmpty() ||
+      layer->filter())
+    return true;
+
+  int num_descendants_that_draw_content =
+      layer->draw_properties().num_descendants_that_draw_content;
+
+  // If the layer flattens its subtree (i.e. the layer doesn't preserve-3d), but
+  // it is treated as a 3D object by its parent (i.e. parent does preserve-3d).
+  if (LayerIsInExisting3DRenderingContext(layer) && !layer->preserves_3d() &&
+      num_descendants_that_draw_content > 0) {
+    TRACE_EVENT_INSTANT0(
+        "cc",
+        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface flattening");
+    return true;
+  }
+
+  // If the layer clips its descendants but it is not axis-aligned with respect
+  // to its parent.
+  bool layer_clips_external_content =
+      LayerClipsSubtree(layer) || layer->HasDelegatedContent();
+  if (layer_clips_external_content && !axis_aligned_with_respect_to_parent &&
+      !layer->draw_properties().descendants_can_clip_selves) {
+    TRACE_EVENT_INSTANT0(
+        "cc",
+        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface clipping");
+    return true;
+  }
+
+  // If the layer has some translucency and does not have a preserves-3d
+  // transform style.  This condition only needs a render surface if two or more
+  // layers in the subtree overlap. But checking layer overlaps is unnecessarily
+  // costly so instead we conservatively create a surface whenever at least two
+  // layers draw content for this subtree.
+  bool at_least_two_layers_in_subtree_draw_content =
+      num_descendants_that_draw_content > 0 &&
+      (layer->DrawsContent() || num_descendants_that_draw_content > 1);
+
+  if (layer->opacity() != 1.f && !layer->preserves_3d() &&
+      at_least_two_layers_in_subtree_draw_content) {
+    TRACE_EVENT_INSTANT0(
+        "cc",
+        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface opacity");
+    return true;
+  }
+
+  return false;
+}
+
+gfx::Transform ComputeScrollCompensationForThisLayer(
+    LayerImpl* scrolling_layer,
+    const gfx::Transform& parent_matrix) {
+  // For every layer that has non-zero scroll_delta, we have to compute a
+  // transform that can undo the scroll_delta translation. In particular, we
+  // want this matrix to premultiply a fixed-position layer's parent_matrix, so
+  // we design this transform in three steps as follows. The steps described
+  // here apply from right-to-left, so Step 1 would be the right-most matrix:
+  //
+  //     Step 1. transform from target surface space to the exact space where
+  //           scroll_delta is actually applied.
+  //           -- this is inverse of the matrix in step 3
+  //     Step 2. undo the scroll_delta
+  //           -- this is just a translation by scroll_delta.
+  //     Step 3. transform back to target surface space.
+  //           -- this transform is the "partial_layer_origin_transform" =
+  //           (parent_matrix * scale(layer->pageScaleDelta()));
+  //
+  // These steps create a matrix that both start and end in targetSurfaceSpace.
+  // So this matrix can pre-multiply any fixed-position layer's draw_transform
+  // to undo the scroll_deltas -- as long as that fixed position layer is fixed
+  // onto the same render_target as this scrolling_layer.
+  //
+
+  gfx::Transform partial_layer_origin_transform = parent_matrix;
+  partial_layer_origin_transform.PreconcatTransform(
+      scrolling_layer->impl_transform());
+
+  gfx::Transform scroll_compensation_for_this_layer =
+      partial_layer_origin_transform;        // Step 3
+  scroll_compensation_for_this_layer.Translate(
+      scrolling_layer->scroll_delta().x(),
+      scrolling_layer->scroll_delta().y());  // Step 2
+
+  gfx::Transform inverse_partial_layer_origin_transform(
+      gfx::Transform::kSkipInitialization);
+  if (!partial_layer_origin_transform.GetInverse(
+          &inverse_partial_layer_origin_transform)) {
+    // TODO(shawnsingh): Either we need to handle uninvertible transforms
+    // here, or DCHECK that the transform is invertible.
+  }
+  scroll_compensation_for_this_layer.PreconcatTransform(
+      inverse_partial_layer_origin_transform);  // Step 1
+  return scroll_compensation_for_this_layer;
+}
+
+gfx::Transform ComputeScrollCompensationMatrixForChildren(
+    Layer* current_layer,
+    const gfx::Transform& current_parent_matrix,
+    const gfx::Transform& current_scroll_compensation) {
+  // The main thread (i.e. Layer) does not need to worry about scroll
+  // compensation.  So we can just return an identity matrix here.
+  return gfx::Transform();
+}
+
+gfx::Transform ComputeScrollCompensationMatrixForChildren(
+    LayerImpl* layer,
+    const gfx::Transform& parent_matrix,
+    const gfx::Transform& current_scroll_compensation_matrix) {
+  // "Total scroll compensation" is the transform needed to cancel out all
+  // scroll_delta translations that occurred since the nearest container layer,
+  // even if there are render_surfaces in-between.
+  //
+  // There are some edge cases to be aware of, that are not explicit in the
+  // code:
+  //  - A layer that is both a fixed-position and container should not be its
+  //  own container, instead, that means it is fixed to an ancestor, and is a
+  //  container for any fixed-position descendants.
+  //  - A layer that is a fixed-position container and has a render_surface
+  //  should behave the same as a container without a render_surface, the
+  //  render_surface is irrelevant in that case.
+  //  - A layer that does not have an explicit container is simply fixed to the
+  //  viewport.  (i.e. the root render_surface.)
+  //  - If the fixed-position layer has its own render_surface, then the
+  //  render_surface is the one who gets fixed.
+  //
+  // This function needs to be called AFTER layers create their own
+  // render_surfaces.
+  //
+
+  // Avoid the overheads (including stack allocation and matrix
+  // initialization/copy) if we know that the scroll compensation doesn't need
+  // to be reset or adjusted.
+  if (!layer->is_container_for_fixed_position_layers() &&
+      layer->scroll_delta().IsZero() && !layer->render_surface())
+    return current_scroll_compensation_matrix;
+
+  // Start as identity matrix.
+  gfx::Transform next_scroll_compensation_matrix;
+
+  // If this layer is not a container, then it inherits the existing scroll
+  // compensations.
+  if (!layer->is_container_for_fixed_position_layers())
+    next_scroll_compensation_matrix = current_scroll_compensation_matrix;
+
+  // If the current layer has a non-zero scroll_delta, then we should compute
+  // its local scrollCompensation and accumulate it to the
+  // next_scroll_compensation_matrix.
+  if (!layer->scroll_delta().IsZero()) {
+    gfx::Transform scroll_compensation_for_this_layer =
+        ComputeScrollCompensationForThisLayer(layer, parent_matrix);
+    next_scroll_compensation_matrix.PreconcatTransform(
+        scroll_compensation_for_this_layer);
+  }
+
+  // If the layer created its own render_surface, we have to adjust
+  // next_scroll_compensation_matrix.  The adjustment allows us to continue
+  // using the scrollCompensation on the next surface.
+  //  Step 1 (right-most in the math): transform from the new surface to the
+  //  original ancestor surface
+  //  Step 2: apply the scroll compensation
+  //  Step 3: transform back to the new surface.
+  if (layer->render_surface() &&
+      !next_scroll_compensation_matrix.IsIdentity()) {
+    gfx::Transform inverse_surface_draw_transform(
+        gfx::Transform::kSkipInitialization);
+    if (!layer->render_surface()->draw_transform().GetInverse(
+            &inverse_surface_draw_transform)) {
+      // TODO(shawnsingh): Either we need to handle uninvertible transforms
+      // here, or DCHECK that the transform is invertible.
     }
-
-    // If the layer clips its descendants but it is not axis-aligned with respect to its parent.
-    bool layerClipsExternalContent = layerClipsSubtree(layer) || layer->HasDelegatedContent();
-    if (layerClipsExternalContent && !axisAlignedWithRespectToParent && !layer->draw_properties().descendants_can_clip_selves)
-    {
-        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface clipping");
-        return true;
+    next_scroll_compensation_matrix =
+        inverse_surface_draw_transform * next_scroll_compensation_matrix *
+        layer->render_surface()->draw_transform();
+  }
+
+  return next_scroll_compensation_matrix;
+}
+
+template <typename LayerType>
+static inline void CalculateContentsScale(LayerType* layer,
+                                          float contents_scale,
+                                          bool animating_transform_to_screen) {
+  layer->CalculateContentsScale(contents_scale,
+                                animating_transform_to_screen,
+                                &layer->draw_properties().contents_scale_x,
+                                &layer->draw_properties().contents_scale_y,
+                                &layer->draw_properties().content_bounds);
+
+  LayerType* mask_layer = layer->mask_layer();
+  if (mask_layer) {
+    mask_layer->CalculateContentsScale(
+        contents_scale,
+        animating_transform_to_screen,
+        &mask_layer->draw_properties().contents_scale_x,
+        &mask_layer->draw_properties().contents_scale_y,
+        &mask_layer->draw_properties().content_bounds);
+  }
+
+  LayerType* replica_mask_layer =
+      layer->replica_layer() ? layer->replica_layer()->mask_layer() : NULL;
+  if (replica_mask_layer) {
+    replica_mask_layer->CalculateContentsScale(
+        contents_scale,
+        animating_transform_to_screen,
+        &replica_mask_layer->draw_properties().contents_scale_x,
+        &replica_mask_layer->draw_properties().contents_scale_y,
+        &replica_mask_layer->draw_properties().content_bounds);
+  }
+}
+
+static inline void UpdateLayerContentsScale(
+    LayerImpl* layer,
+    const gfx::Transform& combined_transform,
+    float device_scale_factor,
+    float page_scale_factor,
+    bool animating_transform_to_screen) {
+  gfx::Vector2dF transform_scale = MathUtil::ComputeTransform2dScaleComponents(
+      combined_transform, device_scale_factor * page_scale_factor);
+  float contents_scale = std::max(transform_scale.x(), transform_scale.y());
+  CalculateContentsScale(layer, contents_scale, animating_transform_to_screen);
+}
+
+static inline void UpdateLayerContentsScale(
+    Layer* layer,
+    const gfx::Transform& combined_transform,
+    float device_scale_factor,
+    float page_scale_factor,
+    bool animating_transform_to_screen) {
+  float raster_scale = layer->raster_scale();
+
+  if (layer->automatically_compute_raster_scale()) {
+    gfx::Vector2dF transform_scale =
+        MathUtil::ComputeTransform2dScaleComponents(combined_transform, 0.f);
+    float combined_scale = std::max(transform_scale.x(), transform_scale.y());
+    float ideal_raster_scale = combined_scale / device_scale_factor;
+    if (!layer->bounds_contain_page_scale())
+      ideal_raster_scale /= page_scale_factor;
+
+    bool need_to_set_raster_scale = !raster_scale;
+
+    // If we've previously saved a raster_scale but the ideal changes, things
+    // are unpredictable and we should just use 1.
+    if (raster_scale && raster_scale != 1.f &&
+        ideal_raster_scale != raster_scale) {
+      ideal_raster_scale = 1.f;
+      need_to_set_raster_scale = true;
     }
 
-    // If the layer has some translucency and does not have a preserves-3d transform style.
-    // This condition only needs a render surface if two or more layers in the
-    // subtree overlap. But checking layer overlaps is unnecessarily costly so
-    // instead we conservatively create a surface whenever at least two layers
-    // draw content for this subtree.
-    bool atLeastTwoLayersInSubtreeDrawContent = numDescendantsThatDrawContent > 0 && (layer->DrawsContent() || numDescendantsThatDrawContent > 1);
-
-    if (layer->opacity() != 1.f && !layer->preserves_3d() && atLeastTwoLayersInSubtreeDrawContent) {
-        TRACE_EVENT_INSTANT0("cc", "LayerTreeHostCommon::requireSurface opacity");
-        return true;
+    if (need_to_set_raster_scale) {
+      bool use_and_save_ideal_scale =
+          ideal_raster_scale >= 1.f && !animating_transform_to_screen;
+      if (use_and_save_ideal_scale) {
+        raster_scale = ideal_raster_scale;
+        layer->SetRasterScale(raster_scale);
+      }
     }
-
-    return false;
-}
-
-gfx::Transform computeScrollCompensationForThisLayer(LayerImpl* scrollingLayer, const gfx::Transform& parentMatrix)
-{
-    // For every layer that has non-zero scrollDelta, we have to compute a transform that can undo the
-    // scrollDelta translation. In particular, we want this matrix to premultiply a fixed-position layer's
-    // parentMatrix, so we design this transform in three steps as follows. The steps described here apply
-    // from right-to-left, so Step 1 would be the right-most matrix:
-    //
-    //     Step 1. transform from target surface space to the exact space where scrollDelta is actually applied.
-    //           -- this is inverse of the matrix in step 3
-    //     Step 2. undo the scrollDelta
-    //           -- this is just a translation by scrollDelta.
-    //     Step 3. transform back to target surface space.
-    //           -- this transform is the "partialLayerOriginTransform" = (parentMatrix * scale(layer->pageScaleDelta()));
-    //
-    // These steps create a matrix that both start and end in targetSurfaceSpace. So this matrix can
-    // pre-multiply any fixed-position layer's drawTransform to undo the scrollDeltas -- as long as
-    // that fixed position layer is fixed onto the same renderTarget as this scrollingLayer.
-    //
-
-    gfx::Transform partialLayerOriginTransform = parentMatrix;
-    partialLayerOriginTransform.PreconcatTransform(scrollingLayer->impl_transform());
-
-    gfx::Transform scrollCompensationForThisLayer = partialLayerOriginTransform; // Step 3
-    scrollCompensationForThisLayer.Translate(scrollingLayer->scroll_delta().x(), scrollingLayer->scroll_delta().y()); // Step 2
-
-    gfx::Transform inversePartialLayerOriginTransform(gfx::Transform::kSkipInitialization);
-    if (!partialLayerOriginTransform.GetInverse(&inversePartialLayerOriginTransform)) {
+  }
+
+  if (!raster_scale)
+    raster_scale = 1.f;
+
+  float contents_scale = raster_scale * device_scale_factor;
+  if (!layer->bounds_contain_page_scale())
+    contents_scale *= page_scale_factor;
+
+  CalculateContentsScale(layer, contents_scale, animating_transform_to_screen);
+}
+
+template <typename LayerType, typename LayerList>
+static inline void RemoveSurfaceForEarlyExit(
+    LayerType* layer_to_remove,
+    LayerList& render_surface_layer_list) {
+  DCHECK(layer_to_remove->render_surface());
+  // Technically, we know that the layer we want to remove should be
+  // at the back of the render_surface_layer_list. However, we have had
+  // bugs before that added unnecessary layers here
+  // (https://bugs.webkit.org/show_bug.cgi?id=74147), but that causes
+  // things to crash. So here we proactively remove any additional
+  // layers from the end of the list.
+  while (render_surface_layer_list->back() != layer_to_remove) {
+    render_surface_layer_list->back()->ClearRenderSurface();
+    render_surface_layer_list->pop_back();
+  }
+  DCHECK_EQ(render_surface_layer_list->back(), layer_to_remove);
+  render_surface_layer_list->pop_back();
+  layer_to_remove->ClearRenderSurface();
+}
+
+// Recursively walks the layer tree to compute any information that is needed
+// before doing the main recursion.
+template <typename LayerType>
+static void PreCalculateMetaInformation(LayerType* layer) {
+  if (layer->HasDelegatedContent()) {
+    // Layers with delegated content need to be treated as if they have as many
+    // children as the number of layers they own delegated quads for. Since we
+    // don't know this number right now, we choose one that acts like infinity
+    // for our purposes.
+    layer->draw_properties().num_descendants_that_draw_content = 1000;
+    layer->draw_properties().descendants_can_clip_selves = false;
+    return;
+  }
+
+  int num_descendants_that_draw_content = 0;
+  bool descendants_can_clip_selves = true;
+  bool sublayer_transform_prevents_clip =
+      !layer->sublayer_transform().IsPositiveScaleOrTranslation();
+
+  for (size_t i = 0; i < layer->children().size(); ++i) {
+    LayerType* child_layer = layer->children()[i];
+    PreCalculateMetaInformation<LayerType>(child_layer);
+
+    num_descendants_that_draw_content += child_layer->DrawsContent() ? 1 : 0;
+    num_descendants_that_draw_content +=
+        child_layer->draw_properties().num_descendants_that_draw_content;
+
+    if ((child_layer->DrawsContent() && !child_layer->CanClipSelf()) ||
+        !child_layer->draw_properties().descendants_can_clip_selves ||
+        sublayer_transform_prevents_clip ||
+        !child_layer->transform().IsPositiveScaleOrTranslation())
+      descendants_can_clip_selves = false;
+  }
+
+  layer->draw_properties().num_descendants_that_draw_content =
+      num_descendants_that_draw_content;
+  layer->draw_properties().descendants_can_clip_selves =
+      descendants_can_clip_selves;
+}
+
+static void RoundTranslationComponents(gfx::Transform* transform) {
+  transform->matrix().
+      setDouble(0, 3, MathUtil::Round(transform->matrix().getDouble(0, 3)));
+  transform->matrix().
+      setDouble(1, 3, MathUtil::Round(transform->matrix().getDouble(1, 3)));
+}
+
+// Recursively walks the layer tree starting at the given node and computes all
+// the necessary transformations, clipRects, render surfaces, etc.
+template <typename LayerType, typename LayerList, typename RenderSurfaceType>
+static void CalculateDrawPropertiesInternal(
+    LayerType* layer,
+    const gfx::Transform& parent_matrix,
+    const gfx::Transform& full_hierarchy_matrix,
+    const gfx::Transform& current_scroll_compensation_matrix,
+    gfx::Rect clip_rect_from_ancestor,
+    gfx::Rect clip_rect_from_ancestor_in_descendant_space,
+    bool ancestor_clips_subtree,
+    RenderSurfaceType* nearest_ancestor_that_moves_pixels,
+    LayerList* render_surface_layer_list,
+    LayerList* layer_list,
+    LayerSorter* layer_sorter,
+    int max_texture_size,
+    float device_scale_factor,
+    float page_scale_factor,
+    bool subtree_can_use_lcd_text,
+    gfx::Rect* drawable_content_rect_of_subtree,
+    bool update_tile_priorities) {
+  // This function computes the new matrix transformations recursively for this
+  // layer and all its descendants. It also computes the appropriate render
+  // surfaces.
+  // Some important points to remember:
+  //
+  // 0. Here, transforms are notated in Matrix x Vector order, and in words we
+  // describe what the transform does from left to right.
+  //
+  // 1. In our terminology, the "layer origin" refers to the top-left corner of
+  // a layer, and the positive Y-axis points downwards. This interpretation is
+  // valid because the orthographic projection applied at draw time flips the Y
+  // axis appropriately.
+  //
+  // 2. The anchor point, when given as a PointF object, is specified in "unit
+  // layer space", where the bounds of the layer map to [0, 1]. However, as a
+  // Transform object, the transform to the anchor point is specified in "layer
+  // space", where the bounds of the layer map to [bounds.width(),
+  // bounds.height()].
+  //
+  // 3. Definition of various transforms used:
+  //        M[parent] is the parent matrix, with respect to the nearest render
+  //        surface, passed down recursively.
+  //
+  //        M[root] is the full hierarchy, with respect to the root, passed down
+  //        recursively.
+  //
+  //        Tr[origin] is the translation matrix from the parent's origin to
+  //        this layer's origin.
+  //
+  //        Tr[origin2anchor] is the translation from the layer's origin to its
+  //        anchor point
+  //
+  //        Tr[origin2center] is the translation from the layer's origin to its
+  //        center
+  //
+  //        M[layer] is the layer's matrix (applied at the anchor point)
+  //
+  //        M[sublayer] is the layer's sublayer transform (also applied at the
+  //        layer's anchor point)
+  //
+  //        S[layer2content] is the ratio of a layer's ContentBounds() to its
+  //        Bounds().
+  //
+  //    Some composite transforms can help in understanding the sequence of
+  //    transforms:
+  //        compositeLayerTransform = Tr[origin2anchor] * M[layer] *
+  //        Tr[origin2anchor].inverse()
+  //
+  //        compositeSublayerTransform = Tr[origin2anchor] * M[sublayer] *
+  //        Tr[origin2anchor].inverse()
+  //
+  // 4. When a layer (or render surface) is drawn, it is drawn into a "target
+  // render surface". Therefore the draw transform does not necessarily
+  // transform from screen space to local layer space. Instead, the draw
+  // transform is the transform between the "target render surface space" and
+  // local layer space. Note that render surfaces, except for the root, also
+  // draw themselves into a different target render surface, and so their draw
+  // transform and origin transforms are also described with respect to the
+  // target.
+  //
+  // Using these definitions, then:
+  //
+  // The draw transform for the layer is:
+  //        M[draw] = M[parent] * Tr[origin] * compositeLayerTransform *
+  //            S[layer2content] = M[parent] * Tr[layer->Position() + anchor] *
+  //            M[layer] * Tr[anchor2origin] * S[layer2content]
+  //
+  //        Interpreting the math left-to-right, this transforms from the
+  //        layer's render surface to the origin of the layer in content space.
+  //
+  // The screen space transform is:
+  //        M[screenspace] = M[root] * Tr[origin] * compositeLayerTransform *
+  //            S[layer2content]
+  //                       = M[root] * Tr[layer->Position() + anchor] * M[layer]
+  //                           * Tr[anchor2origin] * S[layer2content]
+  //
+  //        Interpreting the math left-to-right, this transforms from the root
+  //        render surface's content space to the origin of the layer in content
+  //        space.
+  //
+  // The transform hierarchy that is passed on to children (i.e. the child's
+  // parent_matrix) is:
+  //        M[parent]_for_child = M[parent] * Tr[origin] *
+  //            compositeLayerTransform * compositeSublayerTransform
+  //                            = M[parent] * Tr[layer->Position() + anchor] *
+  //                                M[layer] * Tr[anchor2origin] *
+  //                                compositeSublayerTransform
+  //
+  //        and a similar matrix for the full hierarchy with respect to the
+  //        root.
+  //
+  // Finally, note that the final matrix used by the shader for the layer is P *
+  // M[draw] * S . This final product is computed in drawTexturedQuad(), where:
+  //        P is the projection matrix
+  //        S is the scale adjustment (to scale up a canonical quad to the
+  //            layer's size)
+  //
+  // When a render surface has a replica layer, that layer's transform is used
+  // to draw a second copy of the surface.  gfx::Transforms named here are
+  // relative to the surface, unless they specify they are relative to the
+  // replica layer.
+  //
+  // We will denote a scale by device scale S[deviceScale]
+  //
+  // The render surface draw transform to its target surface origin is:
+  //        M[surfaceDraw] = M[owningLayer->Draw]
+  //
+  // The render surface origin transform to its the root (screen space) origin
+  // is:
+  //        M[surface2root] =  M[owningLayer->screenspace] *
+  //            S[deviceScale].inverse()
+  //
+  // The replica draw transform to its target surface origin is:
+  //        M[replicaDraw] = S[deviceScale] * M[surfaceDraw] *
+  //            Tr[replica->Position() + replica->anchor()] * Tr[replica] *
+  //            Tr[origin2anchor].inverse() * S[contents_scale].inverse()
+  //
+  // The replica draw transform to the root (screen space) origin is:
+  //        M[replica2root] = M[surface2root] * Tr[replica->Position()] *
+  //            Tr[replica] * Tr[origin2anchor].inverse()
+  //
+
+  // If we early-exit anywhere in this function, the drawableContentRect of this
+  // subtree should be considered empty.
+  *drawable_content_rect_of_subtree = gfx::Rect();
+
+  // The root layer cannot skip calcDrawProperties.
+  if (!IsRootLayer(layer) && SubtreeShouldBeSkipped(layer))
+    return;
+
+  // As this function proceeds, these are the properties for the current
+  // layer that actually get computed. To avoid unnecessary copies
+  // (particularly for matrices), we do computations directly on these values
+  // when possible.
+  DrawProperties<LayerType, RenderSurfaceType>& layer_draw_properties =
+      layer->draw_properties();
+
+  gfx::Rect clip_rect_for_subtree;
+  bool subtree_should_be_clipped = false;
+
+  // This value is cached on the stack so that we don't have to inverse-project
+  // the surface's clipRect redundantly for every layer. This value is the
+  // same as the surface's clipRect, except that instead of being described
+  // in the target surface space (i.e. the ancestor surface space), it is
+  // described in the current surface space.
+  gfx::Rect clip_rect_for_subtree_in_descendant_space;
+
+  float accumulated_draw_opacity = layer->opacity();
+  bool animating_opacity_to_target = layer->OpacityIsAnimating();
+  bool animating_opacity_to_screen = animating_opacity_to_target;
+  if (layer->parent()) {
+    accumulated_draw_opacity *= layer->parent()->draw_opacity();
+    animating_opacity_to_target |= layer->parent()->draw_opacity_is_animating();
+    animating_opacity_to_screen |=
+        layer->parent()->screen_space_opacity_is_animating();
+  }
+
+  bool animating_transform_to_target = layer->TransformIsAnimating();
+  bool animating_transform_to_screen = animating_transform_to_target;
+  if (layer->parent()) {
+    animating_transform_to_target |=
+        layer->parent()->draw_transform_is_animating();
+    animating_transform_to_screen |=
+        layer->parent()->screen_space_transform_is_animating();
+  }
+
+  gfx::Size bounds = layer->bounds();
+  gfx::PointF anchor_point = layer->anchor_point();
+  gfx::PointF position = layer->position() - layer->scroll_delta();
+
+  gfx::Transform combined_transform = parent_matrix;
+  if (!layer->transform().IsIdentity()) {
+    // LT = Tr[origin] * Tr[origin2anchor]
+    combined_transform.Translate3d(
+        position.x() + anchor_point.x() * bounds.width(),
+        position.y() + anchor_point.y() * bounds.height(),
+        layer->anchor_point_z());
+    // LT = Tr[origin] * Tr[origin2anchor] * M[layer]
+    combined_transform.PreconcatTransform(layer->transform());
+    // LT = Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2origin]
+    combined_transform.Translate3d(-anchor_point.x() * bounds.width(),
+                                   -anchor_point.y() * bounds.height(),
+                                   -layer->anchor_point_z());
+  } else {
+    combined_transform.Translate(position.x(), position.y());
+  }
+
+  // The layer's contentsSize is determined from the combined_transform, which
+  // then informs the layer's draw_transform.
+  UpdateLayerContentsScale(layer,
+                           combined_transform,
+                           device_scale_factor,
+                           page_scale_factor,
+                           animating_transform_to_screen);
+
+  // If there is a transformation from the impl thread then it should be at
+  // the start of the combined_transform, but we don't want it to affect the
+  // computation of contents_scale above.
+  // Note carefully: this is Concat, not Preconcat (implTransform *
+  // combined_transform).
+  combined_transform.ConcatTransform(layer->impl_transform());
+
+  if (!animating_transform_to_target && layer->scrollable() &&
+      combined_transform.IsScaleOrTranslation()) {
+    // Align the scrollable layer's position to screen space pixels to avoid
+    // blurriness.  To avoid side-effects, do this only if the transform is
+    // simple.
+    RoundTranslationComponents(&combined_transform);
+  }
+
+  if (layer->fixed_to_container_layer()) {
+    // Special case: this layer is a composited fixed-position layer; we need to
+    // explicitly compensate for all ancestors' nonzero scroll_deltas to keep
+    // this layer fixed correctly.
+    // Note carefully: this is Concat, not Preconcat
+    // (current_scroll_compensation * combined_transform).
+    combined_transform.ConcatTransform(current_scroll_compensation_matrix);
+  }
+
+  // The draw_transform that gets computed below is effectively the layer's
+  // draw_transform, unless the layer itself creates a render_surface. In that
+  // case, the render_surface re-parents the transforms.
+  layer_draw_properties.target_space_transform = combined_transform;
+  // M[draw] = M[parent] * LT * S[layer2content]
+  layer_draw_properties.target_space_transform.Scale
+      (1.f / layer->contents_scale_x(), 1.f / layer->contents_scale_y());
+
+  // layerScreenSpaceTransform represents the transform between root layer's
+  // "screen space" and local content space.
+  layer_draw_properties.screen_space_transform = full_hierarchy_matrix;
+  if (!layer->preserves_3d())
+    layer_draw_properties.screen_space_transform.FlattenTo2d();
+  layer_draw_properties.screen_space_transform.PreconcatTransform
+      (layer_draw_properties.target_space_transform);
+
+  // Adjusting text AA method during animation may cause repaints, which in-turn
+  // causes jank.
+  bool adjust_text_aa =
+      !animating_opacity_to_screen && !animating_transform_to_screen;
+  // To avoid color fringing, LCD text should only be used on opaque layers with
+  // just integral translation.
+  bool layer_can_use_lcd_text =
+      subtree_can_use_lcd_text && (accumulated_draw_opacity == 1.f) &&
+      layer_draw_properties.target_space_transform.
+          IsIdentityOrIntegerTranslation();
+
+  gfx::RectF content_rect(gfx::PointF(), layer->content_bounds());
+
+  // full_hierarchy_matrix is the matrix that transforms objects between screen
+  // space (except projection matrix) and the most recent RenderSurfaceImpl's
+  // space.  next_hierarchy_matrix will only change if this layer uses a new
+  // RenderSurfaceImpl, otherwise remains the same.
+  gfx::Transform next_hierarchy_matrix = full_hierarchy_matrix;
+  gfx::Transform sublayer_matrix;
+
+  gfx::Vector2dF render_surface_sublayer_scale =
+      MathUtil::ComputeTransform2dScaleComponents(
+          combined_transform, device_scale_factor * page_scale_factor);
+
+  if (SubtreeShouldRenderToSeparateSurface(
+          layer, combined_transform.IsScaleOrTranslation())) {
+    // Check back-face visibility before continuing with this surface and its
+    // subtree
+    if (!layer->double_sided() && TransformToParentIsKnown(layer) &&
+        IsSurfaceBackFaceVisible(layer, combined_transform))
+      return;
+
+    if (!layer->render_surface())
+      layer->CreateRenderSurface();
+
+    RenderSurfaceType* render_surface = layer->render_surface();
+    render_surface->ClearLayerLists();
+
+    // The owning layer's draw transform has a scale from content to layer
+    // space which we do not want; so here we use the combined_transform
+    // instead of the draw_transform. However, we do need to add a different
+    // scale factor that accounts for the surface's pixel dimensions.
+    combined_transform.Scale(1.0 / render_surface_sublayer_scale.x(),
+                             1.0 / render_surface_sublayer_scale.y());
+    render_surface->SetDrawTransform(combined_transform);
+
+    // The owning layer's transform was re-parented by the surface, so the
+    // layer's new draw_transform only needs to scale the layer to surface
+    // space.
+    layer_draw_properties.target_space_transform.MakeIdentity();
+    layer_draw_properties.target_space_transform.
+        Scale(render_surface_sublayer_scale.x() / layer->contents_scale_x(),
+              render_surface_sublayer_scale.y() / layer->contents_scale_y());
+
+    // Inside the surface's subtree, we scale everything to the owning layer's
+    // scale.  The sublayer matrix transforms layer rects into target surface
+    // content space.
+    DCHECK(sublayer_matrix.IsIdentity());
+    sublayer_matrix.Scale(render_surface_sublayer_scale.x(),
+                          render_surface_sublayer_scale.y());
+
+    // The opacity value is moved from the layer to its surface, so that the
+    // entire subtree properly inherits opacity.
+    render_surface->SetDrawOpacity(accumulated_draw_opacity);
+    render_surface->SetDrawOpacityIsAnimating(animating_opacity_to_target);
+    animating_opacity_to_target = false;
+    layer_draw_properties.opacity = 1.f;
+    layer_draw_properties.opacity_is_animating = animating_opacity_to_target;
+    layer_draw_properties.screen_space_opacity_is_animating =
+        animating_opacity_to_screen;
+
+    render_surface->SetTargetSurfaceTransformsAreAnimating(
+        animating_transform_to_target);
+    render_surface->SetScreenSpaceTransformsAreAnimating(
+        animating_transform_to_screen);
+    animating_transform_to_target = false;
+    layer_draw_properties.target_space_transform_is_animating =
+        animating_transform_to_target;
+    layer_draw_properties.screen_space_transform_is_animating =
+        animating_transform_to_screen;
+
+    // Update the aggregate hierarchy matrix to include the transform of the
+    // newly created RenderSurfaceImpl.
+    next_hierarchy_matrix.PreconcatTransform(render_surface->draw_transform());
+
+    // The new render_surface here will correctly clip the entire subtree. So,
+    // we do not need to continue propagating the clipping state further down
+    // the tree. This way, we can avoid transforming clipRects from ancestor
+    // target surface space to current target surface space that could cause
+    // more w < 0 headaches.
+    subtree_should_be_clipped = false;
+
+    if (layer->mask_layer()) {
+      DrawProperties<LayerType, RenderSurfaceType>& mask_layer_draw_properties =
+          layer->mask_layer()->draw_properties();
+      mask_layer_draw_properties.render_target = layer;
+      mask_layer_draw_properties.visible_content_rect =
+          gfx::Rect(gfx::Point(), layer->content_bounds());
+    }
+
+    if (layer->replica_layer() && layer->replica_layer()->mask_layer()) {
+      DrawProperties<LayerType, RenderSurfaceType>&
+      replica_mask_draw_properties =
+          layer->replica_layer()->mask_layer()->draw_properties();
+      replica_mask_draw_properties.render_target = layer;
+      replica_mask_draw_properties.visible_content_rect =
+          gfx::Rect(gfx::Point(), layer->content_bounds());
+    }
+
+    // TODO(senorblanco): make this smarter for the SkImageFilter case (check
+    // for pixel-moving filters)
+    if (layer->filters().hasFilterThatMovesPixels() || layer->filter())
+      nearest_ancestor_that_moves_pixels = render_surface;
+
+    // The render surface clipRect is expressed in the space where this surface
+    // draws, i.e. the same space as clip_rect_from_ancestor.
+    render_surface->SetIsClipped(ancestor_clips_subtree);
+    if (ancestor_clips_subtree) {
+      render_surface->SetClipRect(clip_rect_from_ancestor);
+
+      gfx::Transform inverse_surface_draw_transform(
+          gfx::Transform::kSkipInitialization);
+      if (!render_surface->draw_transform().GetInverse(
+              &inverse_surface_draw_transform)) {
         // TODO(shawnsingh): Either we need to handle uninvertible transforms
         // here, or DCHECK that the transform is invertible.
+      }
+      clip_rect_for_subtree_in_descendant_space =
+          gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(
+              inverse_surface_draw_transform, render_surface->clip_rect()));
+    } else {
+      render_surface->SetClipRect(gfx::Rect());
+      clip_rect_for_subtree_in_descendant_space =
+          clip_rect_from_ancestor_in_descendant_space;
     }
-    scrollCompensationForThisLayer.PreconcatTransform(inversePartialLayerOriginTransform); // Step 1
-    return scrollCompensationForThisLayer;
-}
-
-gfx::Transform computeScrollCompensationMatrixForChildren(Layer* current_layer, const gfx::Transform& currentParentMatrix, const gfx::Transform& currentScrollCompensation)
-{
-    // The main thread (i.e. Layer) does not need to worry about scroll compensation.
-    // So we can just return an identity matrix here.
-    return gfx::Transform();
-}
-
-gfx::Transform computeScrollCompensationMatrixForChildren(LayerImpl* layer, const gfx::Transform& parentMatrix, const gfx::Transform& currentScrollCompensationMatrix)
-{
-    // "Total scroll compensation" is the transform needed to cancel out all scrollDelta translations that
-    // occurred since the nearest container layer, even if there are renderSurfaces in-between.
-    //
-    // There are some edge cases to be aware of, that are not explicit in the code:
-    //  - A layer that is both a fixed-position and container should not be its own container, instead, that means
-    //    it is fixed to an ancestor, and is a container for any fixed-position descendants.
-    //  - A layer that is a fixed-position container and has a renderSurface should behave the same as a container
-    //    without a renderSurface, the renderSurface is irrelevant in that case.
-    //  - A layer that does not have an explicit container is simply fixed to the viewport.
-    //    (i.e. the root renderSurface.)
-    //  - If the fixed-position layer has its own renderSurface, then the renderSurface is
-    //    the one who gets fixed.
-    //
-    // This function needs to be called AFTER layers create their own renderSurfaces.
-    //
-
-    // Avoid the overheads (including stack allocation and matrix initialization/copy) if we know that the scroll compensation doesn't need to be reset or adjusted.
-    if (!layer->is_container_for_fixed_position_layers() && layer->scroll_delta().IsZero() && !layer->render_surface())
-        return currentScrollCompensationMatrix;
-
-    // Start as identity matrix.
-    gfx::Transform nextScrollCompensationMatrix;
-
-    // If this layer is not a container, then it inherits the existing scroll compensations.
-    if (!layer->is_container_for_fixed_position_layers())
-        nextScrollCompensationMatrix = currentScrollCompensationMatrix;
-
-    // If the current layer has a non-zero scrollDelta, then we should compute its local scrollCompensation
-    // and accumulate it to the nextScrollCompensationMatrix.
-    if (!layer->scroll_delta().IsZero()) {
-        gfx::Transform scrollCompensationForThisLayer = computeScrollCompensationForThisLayer(layer, parentMatrix);
-        nextScrollCompensationMatrix.PreconcatTransform(scrollCompensationForThisLayer);
+
+    render_surface->SetNearestAncestorThatMovesPixels(
+        nearest_ancestor_that_moves_pixels);
+
+    // If the new render surface is drawn translucent or with a non-integral
+    // translation then the subtree that gets drawn on this render surface
+    // cannot use LCD text.
+    subtree_can_use_lcd_text = layer_can_use_lcd_text;
+
+    render_surface_layer_list->push_back(layer);
+  } else {
+    DCHECK(layer->parent());
+
+    // Note: layer_draw_properties.target_space_transform is computed above,
+    // before this if-else statement.
+    layer_draw_properties.target_space_transform_is_animating =
+        animating_transform_to_target;
+    layer_draw_properties.screen_space_transform_is_animating =
+        animating_transform_to_screen;
+    layer_draw_properties.opacity = accumulated_draw_opacity;
+    layer_draw_properties.opacity_is_animating = animating_opacity_to_target;
+    layer_draw_properties.screen_space_opacity_is_animating =
+        animating_opacity_to_screen;
+    sublayer_matrix = combined_transform;
+
+    layer->ClearRenderSurface();
+
+    // Layers without render_surfaces directly inherit the ancestor's clip
+    // status.
+    subtree_should_be_clipped = ancestor_clips_subtree;
+    if (ancestor_clips_subtree)
+      clip_rect_for_subtree = clip_rect_from_ancestor;
+
+    // The surface's cached clipRect value propagates regardless of what
+    // clipping goes on between layers here.
+    clip_rect_for_subtree_in_descendant_space =
+        clip_rect_from_ancestor_in_descendant_space;
+
+    // Layers that are not their own render_target will render into the target
+    // of their nearest ancestor.
+    layer_draw_properties.render_target = layer->parent()->render_target();
+  }
+
+  if (adjust_text_aa)
+    layer_draw_properties.can_use_lcd_text = layer_can_use_lcd_text;
+
+  gfx::Rect rect_in_target_space = ToEnclosingRect(
+      MathUtil::MapClippedRect(layer->draw_transform(), content_rect));
+
+  if (LayerClipsSubtree(layer)) {
+    subtree_should_be_clipped = true;
+    if (ancestor_clips_subtree && !layer->render_surface()) {
+      clip_rect_for_subtree = clip_rect_from_ancestor;
+      clip_rect_for_subtree.Intersect(rect_in_target_space);
+    } else {
+      clip_rect_for_subtree = rect_in_target_space;
     }
-
-    // If the layer created its own renderSurface, we have to adjust nextScrollCompensationMatrix.
-    // The adjustment allows us to continue using the scrollCompensation on the next surface.
-    //  Step 1 (right-most in the math): transform from the new surface to the original ancestor surface
-    //  Step 2: apply the scroll compensation
-    //  Step 3: transform back to the new surface.
-    if (layer->render_surface() && !nextScrollCompensationMatrix.IsIdentity()) {
-        gfx::Transform inverseSurfaceDrawTransform(gfx::Transform::kSkipInitialization);
-        if (!layer->render_surface()->draw_transform().GetInverse(&inverseSurfaceDrawTransform)) {
-            // TODO(shawnsingh): Either we need to handle uninvertible transforms
-            // here, or DCHECK that the transform is invertible.
-        }
-        nextScrollCompensationMatrix = inverseSurfaceDrawTransform * nextScrollCompensationMatrix * layer->render_surface()->draw_transform();
+  }
+
+  // Flatten to 2D if the layer doesn't preserve 3D.
+  if (!layer->preserves_3d())
+    sublayer_matrix.FlattenTo2d();
+
+  // Apply the sublayer transform at the anchor point of the layer.
+  if (!layer->sublayer_transform().IsIdentity()) {
+    sublayer_matrix.Translate(layer->anchor_point().x() * bounds.width(),
+                              layer->anchor_point().y() * bounds.height());
+    sublayer_matrix.PreconcatTransform(layer->sublayer_transform());
+    sublayer_matrix.Translate(-layer->anchor_point().x() * bounds.width(),
+                              -layer->anchor_point().y() * bounds.height());
+  }
+
+  LayerList& descendants =
+      (layer->render_surface() ? layer->render_surface()->layer_list()
+                               : *layer_list);
+
+  // Any layers that are appended after this point are in the layer's subtree
+  // and should be included in the sorting process.
+  size_t sorting_start_index = descendants.size();
+
+  if (!LayerShouldBeSkipped(layer))
+    descendants.push_back(layer);
+
+  gfx::Transform next_scroll_compensation_matrix =
+      ComputeScrollCompensationMatrixForChildren(
+          layer, parent_matrix, current_scroll_compensation_matrix);
+
+  gfx::Rect accumulated_drawable_content_rect_of_children;
+  for (size_t i = 0; i < layer->children().size(); ++i) {
+    LayerType* child =
+        LayerTreeHostCommon::get_child_as_raw_ptr(layer->children(), i);
+    gfx::Rect drawable_content_rect_of_child_subtree;
+    CalculateDrawPropertiesInternal<LayerType, LayerList, RenderSurfaceType>(
+        child,
+        sublayer_matrix,
+        next_hierarchy_matrix,
+        next_scroll_compensation_matrix,
+        clip_rect_for_subtree,
+        clip_rect_for_subtree_in_descendant_space,
+        subtree_should_be_clipped,
+        nearest_ancestor_that_moves_pixels,
+        render_surface_layer_list,
+        &descendants,
+        layer_sorter,
+        max_texture_size,
+        device_scale_factor,
+        page_scale_factor,
+        subtree_can_use_lcd_text,
+        &drawable_content_rect_of_child_subtree,
+        update_tile_priorities);
+    if (!drawable_content_rect_of_child_subtree.IsEmpty()) {
+      accumulated_drawable_content_rect_of_children.Union(
+          drawable_content_rect_of_child_subtree);
+      if (child->render_surface())
+        descendants.push_back(child);
     }
-
-    return nextScrollCompensationMatrix;
-}
-
-template<typename LayerType>
-static inline void CalculateContentsScale(LayerType* layer, float contentsScale, bool animating_transform_to_screen)
-{
-    layer->CalculateContentsScale(
-        contentsScale,
-        animating_transform_to_screen,
-        &layer->draw_properties().contents_scale_x,
-        &layer->draw_properties().contents_scale_y,
-        &layer->draw_properties().content_bounds);
-
-    LayerType* maskLayer = layer->mask_layer();
-    if (maskLayer)
-    {
-        maskLayer->CalculateContentsScale(
-            contentsScale,
-            animating_transform_to_screen,
-            &maskLayer->draw_properties().contents_scale_x,
-            &maskLayer->draw_properties().contents_scale_y,
-            &maskLayer->draw_properties().content_bounds);
+  }
+
+  if (layer->render_surface() && !IsRootLayer(layer) &&
+      layer->render_surface()->layer_list().empty()) {
+    RemoveSurfaceForEarlyExit(layer, render_surface_layer_list);
+    return;
+  }
+
+  // Compute the total drawableContentRect for this subtree (the rect is in
+  // targetSurface space).
+  gfx::Rect local_drawable_content_rect_of_subtree =
+      accumulated_drawable_content_rect_of_children;
+  if (layer->DrawsContent())
+    local_drawable_content_rect_of_subtree.Union(rect_in_target_space);
+  if (subtree_should_be_clipped)
+    local_drawable_content_rect_of_subtree.Intersect(clip_rect_for_subtree);
+
+  // Compute the layer's drawable content rect (the rect is in targetSurface
+  // space).
+  layer_draw_properties.drawable_content_rect = rect_in_target_space;
+  if (subtree_should_be_clipped) {
+    layer_draw_properties.drawable_content_rect.
+        Intersect(clip_rect_for_subtree);
+  }
+
+  // Tell the layer the rect that is clipped by. In theory we could use a
+  // tighter clipRect here (drawableContentRect), but that actually does not
+  // reduce how much would be drawn, and instead it would create unnecessary
+  // changes to scissor state affecting GPU performance.
+  layer_draw_properties.is_clipped = subtree_should_be_clipped;
+  if (subtree_should_be_clipped) {
+    layer_draw_properties.clip_rect = clip_rect_for_subtree;
+  } else {
+    // Initialize the clipRect to a safe value that will not clip the
+    // layer, just in case clipping is still accidentally used.
+    layer_draw_properties.clip_rect = rect_in_target_space;
+  }
+
+  // Compute the layer's visible content rect (the rect is in content space)
+  layer_draw_properties.visible_content_rect = CalculateVisibleContentRect(
+      layer, clip_rect_for_subtree_in_descendant_space, rect_in_target_space);
+
+  // Compute the remaining properties for the render surface, if the layer has
+  // one.
+  if (IsRootLayer(layer)) {
+    // The root layer's surface's content_rect is always the entire viewport.
+    DCHECK(layer->render_surface());
+    layer->render_surface()->SetContentRect(clip_rect_from_ancestor);
+  } else if (layer->render_surface() && !IsRootLayer(layer)) {
+    RenderSurfaceType* render_surface = layer->render_surface();
+    gfx::Rect clipped_content_rect = local_drawable_content_rect_of_subtree;
+
+    // Don't clip if the layer is reflected as the reflection shouldn't be
+    // clipped. If the layer is animating, then the surface's transform to
+    // its target is not known on the main thread, and we should not use it
+    // to clip.
+    if (!layer->replica_layer() && TransformToParentIsKnown(layer)) {
+      // Note, it is correct to use ancestor_clips_subtree here, because we are
+      // looking at this layer's render_surface, not the layer itself.
+      if (ancestor_clips_subtree && !clipped_content_rect.IsEmpty()) {
+        gfx::Rect surface_clip_rect = LayerTreeHostCommon::CalculateVisibleRect(
+            render_surface->clip_rect(),
+            clipped_content_rect,
+            render_surface->draw_transform());
+        clipped_content_rect.Intersect(surface_clip_rect);
+      }
     }
 
-    LayerType* replicaMaskLayer = layer->replica_layer() ? layer->replica_layer()->mask_layer() : 0;
-    if (replicaMaskLayer)
-    {
-        replicaMaskLayer->CalculateContentsScale(
-            contentsScale,
-            animating_transform_to_screen,
-            &replicaMaskLayer->draw_properties().contents_scale_x,
-            &replicaMaskLayer->draw_properties().contents_scale_y,
-            &replicaMaskLayer->draw_properties().content_bounds);
+    // The RenderSurfaceImpl backing texture cannot exceed the maximum supported
+    // texture size.
+    clipped_content_rect.set_width(
+        std::min(clipped_content_rect.width(), max_texture_size));
+    clipped_content_rect.set_height(
+        std::min(clipped_content_rect.height(), max_texture_size));
+
+    if (clipped_content_rect.IsEmpty()) {
+      render_surface->ClearLayerLists();
+      RemoveSurfaceForEarlyExit(layer, render_surface_layer_list);
+      return;
     }
-}
-
-static inline void updateLayerContentsScale(LayerImpl* layer, const gfx::Transform& combinedTransform, float deviceScaleFactor, float pageScaleFactor, bool animating_transform_to_screen)
-{
-    gfx::Vector2dF transformScale = MathUtil::ComputeTransform2dScaleComponents(combinedTransform, deviceScaleFactor * pageScaleFactor);
-    float contentsScale = std::max(transformScale.x(), transformScale.y());
-    CalculateContentsScale(layer, contentsScale, animating_transform_to_screen);
-}
-
-static inline void updateLayerContentsScale(Layer* layer, const gfx::Transform& combinedTransform, float deviceScaleFactor, float pageScaleFactor, bool animating_transform_to_screen)
-{
-    float rasterScale = layer->raster_scale();
-
-    if (layer->automatically_compute_raster_scale()) {
-        gfx::Vector2dF transformScale = MathUtil::ComputeTransform2dScaleComponents(combinedTransform, 0.f);
-        float combinedScale = std::max(transformScale.x(), transformScale.y());
-        float idealRasterScale = combinedScale / deviceScaleFactor;
-        if (!layer->bounds_contain_page_scale())
-            idealRasterScale /= pageScaleFactor;
-
-        bool needToSetRasterScale = !rasterScale;
-
-        // If we've previously saved a rasterScale but the ideal changes, things are unpredictable and we should just use 1.
-        if (rasterScale && rasterScale != 1.f && idealRasterScale != rasterScale) {
-            idealRasterScale = 1.f;
-            needToSetRasterScale = true;
-        }
-
-        if (needToSetRasterScale) {
-            bool useAndSaveIdealScale = idealRasterScale >= 1.f && !animating_transform_to_screen;
-            if (useAndSaveIdealScale) {
-                rasterScale = idealRasterScale;
-                layer->SetRasterScale(rasterScale);
-            }
-        }
+
+    render_surface->SetContentRect(clipped_content_rect);
+
+    // The owning layer's screen_space_transform has a scale from content to
+    // layer space which we need to undo and replace with a scale from the
+    // surface's subtree into layer space.
+    gfx::Transform screen_space_transform = layer->screen_space_transform();
+    screen_space_transform.Scale(
+        layer->contents_scale_x() / render_surface_sublayer_scale.x(),
+        layer->contents_scale_y() / render_surface_sublayer_scale.y());
+    render_surface->SetScreenSpaceTransform(screen_space_transform);
+
+    if (layer->replica_layer()) {
+      gfx::Transform surface_origin_to_replica_origin_transform;
+      surface_origin_to_replica_origin_transform.Scale(
+          render_surface_sublayer_scale.x(), render_surface_sublayer_scale.y());
+      surface_origin_to_replica_origin_transform.Translate(
+          layer->replica_layer()->position().x() +
+          layer->replica_layer()->anchor_point().x() * bounds.width(),
+          layer->replica_layer()->position().y() +
+          layer->replica_layer()->anchor_point().y() * bounds.height());
+      surface_origin_to_replica_origin_transform.PreconcatTransform(
+          layer->replica_layer()->transform());
+      surface_origin_to_replica_origin_transform.Translate(
+          -layer->replica_layer()->anchor_point().x() * bounds.width(),
+          -layer->replica_layer()->anchor_point().y() * bounds.height());
+      surface_origin_to_replica_origin_transform.Scale(
+          1.0 / render_surface_sublayer_scale.x(),
+          1.0 / render_surface_sublayer_scale.y());
+
+      // Compute the replica's "originTransform" that maps from the replica's
+      // origin space to the target surface origin space.
+      gfx::Transform replica_origin_transform =
+          layer->render_surface()->draw_transform() *
+          surface_origin_to_replica_origin_transform;
+      render_surface->SetReplicaDrawTransform(replica_origin_transform);
+
+      // Compute the replica's "screen_space_transform" that maps from the
+      // replica's origin space to the screen's origin space.
+      gfx::Transform replica_screen_space_transform =
+          layer->render_surface()->screen_space_transform() *
+          surface_origin_to_replica_origin_transform;
+      render_surface->SetReplicaScreenSpaceTransform(
+          replica_screen_space_transform);
     }
-
-    if (!rasterScale)
-        rasterScale = 1.f;
-
-    float contentsScale = rasterScale * deviceScaleFactor;
-    if (!layer->bounds_contain_page_scale())
-        contentsScale *= pageScaleFactor;
-
-    CalculateContentsScale(layer, contentsScale, animating_transform_to_screen);
-}
-
-template<typename LayerType, typename LayerList>
-static inline void removeSurfaceForEarlyExit(LayerType* layerToRemove, LayerList& renderSurfaceLayerList)
-{
-    DCHECK(layerToRemove->render_surface());
-    // Technically, we know that the layer we want to remove should be
-    // at the back of the renderSurfaceLayerList. However, we have had
-    // bugs before that added unnecessary layers here
-    // (https://bugs.webkit.org/show_bug.cgi?id=74147), but that causes
-    // things to crash. So here we proactively remove any additional
-    // layers from the end of the list.
-    while (renderSurfaceLayerList.back() != layerToRemove) {
-        renderSurfaceLayerList.back()->ClearRenderSurface();
-        renderSurfaceLayerList.pop_back();
-    }
-    DCHECK(renderSurfaceLayerList.back() == layerToRemove);
-    renderSurfaceLayerList.pop_back();
-    layerToRemove->ClearRenderSurface();
-}
-
-// Recursively walks the layer tree to compute any information that is needed
-// before doing the main recursion.
-template<typename LayerType>
-static void preCalculateMetaInformation(LayerType* layer)
-{
-    if (layer->HasDelegatedContent()) {
-        // Layers with delegated content need to be treated as if they have as many children as the number
-        // of layers they own delegated quads for. Since we don't know this number right now, we choose
-        // one that acts like infinity for our purposes.
-        layer->draw_properties().num_descendants_that_draw_content = 1000;
-        layer->draw_properties().descendants_can_clip_selves = false;
-        return;
-    }
-
-    int numDescendantsThatDrawContent = 0;
-    bool descendantsCanClipSelves = true;
-    bool sublayerTransformPreventsClip = !layer->sublayer_transform().IsPositiveScaleOrTranslation();
-
-    for (size_t i = 0; i < layer->children().size(); ++i) {
-        LayerType* childLayer = layer->children()[i];
-        preCalculateMetaInformation<LayerType>(childLayer);
-
-        numDescendantsThatDrawContent += childLayer->DrawsContent() ? 1 : 0;
-        numDescendantsThatDrawContent += childLayer->draw_properties().num_descendants_that_draw_content;
-
-        if ((childLayer->DrawsContent() && !childLayer->CanClipSelf()) ||
-            !childLayer->draw_properties().descendants_can_clip_selves ||
-            sublayerTransformPreventsClip ||
-            !childLayer->transform().IsPositiveScaleOrTranslation())
-            descendantsCanClipSelves = false;
-    }
-
-    layer->draw_properties().num_descendants_that_draw_content = numDescendantsThatDrawContent;
-    layer->draw_properties().descendants_can_clip_selves = descendantsCanClipSelves;
-}
-
-static void roundTranslationComponents(gfx::Transform* transform)
-{
-    transform->matrix().setDouble(0, 3, MathUtil::Round(transform->matrix().getDouble(0, 3)));
-    transform->matrix().setDouble(1, 3, MathUtil::Round(transform->matrix().getDouble(1, 3)));
-}
-
-// Recursively walks the layer tree starting at the given node and computes all the
-// necessary transformations, clipRects, render surfaces, etc.
-template<typename LayerType, typename LayerList, typename RenderSurfaceType>
-static void calculateDrawPropertiesInternal(LayerType* layer, const gfx::Transform& parentMatrix,
-    const gfx::Transform& fullHierarchyMatrix, const gfx::Transform& currentScrollCompensationMatrix,
-    const gfx::Rect& clipRectFromAncestor, const gfx::Rect& clipRectFromAncestorInDescendantSpace, bool ancestorClipsSubtree,
-    RenderSurfaceType* nearestAncestorThatMovesPixels, LayerList& renderSurfaceLayerList, LayerList& layerList,
-    LayerSorter* layerSorter, int maxTextureSize, float deviceScaleFactor, float pageScaleFactor, bool subtreeCanUseLCDText,
-    gfx::Rect& drawableContentRectOfSubtree, bool updateTilePriorities)
-{
-    // This function computes the new matrix transformations recursively for this
-    // layer and all its descendants. It also computes the appropriate render surfaces.
-    // Some important points to remember:
-    //
-    // 0. Here, transforms are notated in Matrix x Vector order, and in words we describe what
-    //    the transform does from left to right.
-    //
-    // 1. In our terminology, the "layer origin" refers to the top-left corner of a layer, and the
-    //    positive Y-axis points downwards. This interpretation is valid because the orthographic
-    //    projection applied at draw time flips the Y axis appropriately.
-    //
-    // 2. The anchor point, when given as a PointF object, is specified in "unit layer space",
-    //    where the bounds of the layer map to [0, 1]. However, as a Transform object,
-    //    the transform to the anchor point is specified in "layer space", where the bounds
-    //    of the layer map to [bounds.width(), bounds.height()].
-    //
-    // 3. Definition of various transforms used:
-    //        M[parent] is the parent matrix, with respect to the nearest render surface, passed down recursively.
-    //        M[root] is the full hierarchy, with respect to the root, passed down recursively.
-    //        Tr[origin] is the translation matrix from the parent's origin to this layer's origin.
-    //        Tr[origin2anchor] is the translation from the layer's origin to its anchor point
-    //        Tr[origin2center] is the translation from the layer's origin to its center
-    //        M[layer] is the layer's matrix (applied at the anchor point)
-    //        M[sublayer] is the layer's sublayer transform (also applied at the layer's anchor point)
-    //        S[layer2content] is the ratio of a layer's ContentBounds() to its Bounds().
-    //
-    //    Some composite transforms can help in understanding the sequence of transforms:
-    //        compositeLayerTransform = Tr[origin2anchor] * M[layer] * Tr[origin2anchor].inverse()
-    //        compositeSublayerTransform = Tr[origin2anchor] * M[sublayer] * Tr[origin2anchor].inverse()
-    //
-    // 4. When a layer (or render surface) is drawn, it is drawn into a "target render surface". Therefore the draw
-    //    transform does not necessarily transform from screen space to local layer space. Instead, the draw transform
-    //    is the transform between the "target render surface space" and local layer space. Note that render surfaces,
-    //    except for the root, also draw themselves into a different target render surface, and so their draw
-    //    transform and origin transforms are also described with respect to the target.
-    //
-    // Using these definitions, then:
-    //
-    // The draw transform for the layer is:
-    //        M[draw] = M[parent] * Tr[origin] * compositeLayerTransform * S[layer2content]
-    //                = M[parent] * Tr[layer->Position() + anchor] * M[layer] * Tr[anchor2origin] * S[layer2content]
-    //
-    //        Interpreting the math left-to-right, this transforms from the layer's render surface to the origin of the layer in content space.
-    //
-    // The screen space transform is:
-    //        M[screenspace] = M[root] * Tr[origin] * compositeLayerTransform * S[layer2content]
-    //                       = M[root] * Tr[layer->Position() + anchor] * M[layer] * Tr[anchor2origin] * S[layer2content]
-    //
-    //        Interpreting the math left-to-right, this transforms from the root render surface's content space to the origin of the layer in content space.
-    //
-    // The transform hierarchy that is passed on to children (i.e. the child's parentMatrix) is:
-    //        M[parent]_for_child = M[parent] * Tr[origin] * compositeLayerTransform * compositeSublayerTransform
-    //                            = M[parent] * Tr[layer->Position() + anchor] * M[layer] * Tr[anchor2origin] * compositeSublayerTransform
-    //
-    //        and a similar matrix for the full hierarchy with respect to the root.
-    //
-    // Finally, note that the final matrix used by the shader for the layer is P * M[draw] * S . This final product
-    // is computed in drawTexturedQuad(), where:
-    //        P is the projection matrix
-    //        S is the scale adjustment (to scale up a canonical quad to the layer's size)
-    //
-    // When a render surface has a replica layer, that layer's transform is used to draw a second copy of the surface.
-    // gfx::Transforms named here are relative to the surface, unless they specify they are relative to the replica layer.
-    //
-    // We will denote a scale by device scale S[deviceScale]
-    //
-    // The render surface draw transform to its target surface origin is:
-    //        M[surfaceDraw] = M[owningLayer->Draw]
-    //
-    // The render surface origin transform to its the root (screen space) origin is:
-    //        M[surface2root] =  M[owningLayer->screenspace] * S[deviceScale].inverse()
-    //
-    // The replica draw transform to its target surface origin is:
-    //        M[replicaDraw] = S[deviceScale] * M[surfaceDraw] * Tr[replica->Position() + replica->anchor()] * Tr[replica] * Tr[origin2anchor].inverse() * S[contentsScale].inverse()
-    //
-    // The replica draw transform to the root (screen space) origin is:
-    //        M[replica2root] = M[surface2root] * Tr[replica->Position()] * Tr[replica] * Tr[origin2anchor].inverse()
-    //
-
-    // If we early-exit anywhere in this function, the drawableContentRect of this subtree should be considered empty.
-    drawableContentRectOfSubtree = gfx::Rect();
-
-    // The root layer cannot skip calcDrawProperties.
-    if (!isRootLayer(layer) && subtreeShouldBeSkipped(layer))
-        return;
-
-    // As this function proceeds, these are the properties for the current
-    // layer that actually get computed. To avoid unnecessary copies
-    // (particularly for matrices), we do computations directly on these values
-    // when possible.
-    DrawProperties<LayerType, RenderSurfaceType>& layerDrawProperties = layer->draw_properties();
-
-    gfx::Rect clipRectForSubtree;
-    bool subtreeShouldBeClipped = false;
-
-    // This value is cached on the stack so that we don't have to inverse-project
-    // the surface's clipRect redundantly for every layer. This value is the
-    // same as the surface's clipRect, except that instead of being described
-    // in the target surface space (i.e. the ancestor surface space), it is
-    // described in the current surface space.
-    gfx::Rect clipRectForSubtreeInDescendantSpace;
-
-    float accumulatedDrawOpacity = layer->opacity();
-    bool animatingOpacityToTarget = layer->OpacityIsAnimating();
-    bool animatingOpacityToScreen = animatingOpacityToTarget;
-    if (layer->parent()) {
-        accumulatedDrawOpacity *= layer->parent()->draw_opacity();
-        animatingOpacityToTarget |= layer->parent()->draw_opacity_is_animating();
-        animatingOpacityToScreen |= layer->parent()->screen_space_opacity_is_animating();
-    }
-
-    bool animatingTransformToTarget = layer->TransformIsAnimating();
-    bool animating_transform_to_screen = animatingTransformToTarget;
-    if (layer->parent()) {
-        animatingTransformToTarget |= layer->parent()->draw_transform_is_animating();
-        animating_transform_to_screen |= layer->parent()->screen_space_transform_is_animating();
-    }
-
-    gfx::Size bounds = layer->bounds();
-    gfx::PointF anchorPoint = layer->anchor_point();
-    gfx::PointF position = layer->position() - layer->scroll_delta();
-
-    gfx::Transform combinedTransform = parentMatrix;
-    if (!layer->transform().IsIdentity()) {
-        // LT = Tr[origin] * Tr[origin2anchor]
-        combinedTransform.Translate3d(position.x() + anchorPoint.x() * bounds.width(), position.y() + anchorPoint.y() * bounds.height(), layer->anchor_point_z());
-        // LT = Tr[origin] * Tr[origin2anchor] * M[layer]
-        combinedTransform.PreconcatTransform(layer->transform());
-        // LT = Tr[origin] * Tr[origin2anchor] * M[layer] * Tr[anchor2origin]
-        combinedTransform.Translate3d(-anchorPoint.x() * bounds.width(), -anchorPoint.y() * bounds.height(), -layer->anchor_point_z());
-    } else {
-        combinedTransform.Translate(position.x(), position.y());
-    }
-
-    // The layer's contentsSize is determined from the combinedTransform, which then informs the
-    // layer's drawTransform.
-    updateLayerContentsScale(layer, combinedTransform, deviceScaleFactor, pageScaleFactor, animating_transform_to_screen);
-
-    // If there is a transformation from the impl thread then it should be at
-    // the start of the combinedTransform, but we don't want it to affect the
-    // computation of contentsScale above.
-    // Note carefully: this is Concat, not Preconcat (implTransform * combinedTransform).
-    combinedTransform.ConcatTransform(layer->impl_transform());
-
-    if (!animatingTransformToTarget && layer->scrollable() && combinedTransform.IsScaleOrTranslation()) {
-        // Align the scrollable layer's position to screen space pixels to avoid blurriness.
-        // To avoid side-effects, do this only if the transform is simple.
-        roundTranslationComponents(&combinedTransform);
-    }
-
-    if (layer->fixed_to_container_layer()) {
-        // Special case: this layer is a composited fixed-position layer; we need to
-        // explicitly compensate for all ancestors' nonzero scrollDeltas to keep this layer
-        // fixed correctly.
-        // Note carefully: this is Concat, not Preconcat (currentScrollCompensation * combinedTransform).
-        combinedTransform.ConcatTransform(currentScrollCompensationMatrix);
-    }
-
-    // The drawTransform that gets computed below is effectively the layer's drawTransform, unless
-    // the layer itself creates a renderSurface. In that case, the renderSurface re-parents the transforms.
-    layerDrawProperties.target_space_transform = combinedTransform;
-    // M[draw] = M[parent] * LT * S[layer2content]
-    layerDrawProperties.target_space_transform.Scale(1.0 / layer->contents_scale_x(), 1.0 / layer->contents_scale_y());
-
-    // layerScreenSpaceTransform represents the transform between root layer's "screen space" and local content space.
-    layerDrawProperties.screen_space_transform = fullHierarchyMatrix;
-    if (!layer->preserves_3d())
-        layerDrawProperties.screen_space_transform.FlattenTo2d();
-    layerDrawProperties.screen_space_transform.PreconcatTransform(layerDrawProperties.target_space_transform);
-
-    // Adjusting text AA method during animation may cause repaints, which in-turn causes jank.
-    bool adjustTextAA = !animatingOpacityToScreen && !animating_transform_to_screen;
-    // To avoid color fringing, LCD text should only be used on opaque layers with just integral translation.
-    bool layerCanUseLCDText = subtreeCanUseLCDText &&
-                              (accumulatedDrawOpacity == 1.0) &&
-                              layerDrawProperties.target_space_transform.IsIdentityOrIntegerTranslation();
-
-    gfx::RectF contentRect(gfx::PointF(), layer->content_bounds());
-
-    // fullHierarchyMatrix is the matrix that transforms objects between screen space (except projection matrix) and the most recent RenderSurfaceImpl's space.
-    // nextHierarchyMatrix will only change if this layer uses a new RenderSurfaceImpl, otherwise remains the same.
-    gfx::Transform nextHierarchyMatrix = fullHierarchyMatrix;
-    gfx::Transform sublayerMatrix;
-
-    gfx::Vector2dF renderSurfaceSublayerScale = MathUtil::ComputeTransform2dScaleComponents(combinedTransform, deviceScaleFactor * pageScaleFactor);
-
-    if (subtreeShouldRenderToSeparateSurface(layer, combinedTransform.IsScaleOrTranslation())) {
-        // Check back-face visibility before continuing with this surface and its subtree
-        if (!layer->double_sided() && transformToParentIsKnown(layer) && isSurfaceBackFaceVisible(layer, combinedTransform))
-            return;
-
-        if (!layer->render_surface())
-            layer->CreateRenderSurface();
-
-        RenderSurfaceType* renderSurface = layer->render_surface();
-        renderSurface->ClearLayerLists();
-
-        // The owning layer's draw transform has a scale from content to layer
-        // space which we do not want; so here we use the combinedTransform
-        // instead of the drawTransform. However, we do need to add a different
-        // scale factor that accounts for the surface's pixel dimensions.
-        combinedTransform.Scale(1 / renderSurfaceSublayerScale.x(), 1 / renderSurfaceSublayerScale.y());
-        renderSurface->SetDrawTransform(combinedTransform);
-
-        // The owning layer's transform was re-parented by the surface, so the layer's new drawTransform
-        // only needs to scale the layer to surface space.
-        layerDrawProperties.target_space_transform.MakeIdentity();
-        layerDrawProperties.target_space_transform.Scale(renderSurfaceSublayerScale.x() / layer->contents_scale_x(), renderSurfaceSublayerScale.y() / layer->contents_scale_y());
-
-        // Inside the surface's subtree, we scale everything to the owning layer's scale.
-        // The sublayer matrix transforms layer rects into target
-        // surface content space.
-        DCHECK(sublayerMatrix.IsIdentity());
-        sublayerMatrix.Scale(renderSurfaceSublayerScale.x(), renderSurfaceSublayerScale.y());
-
-        // The opacity value is moved from the layer to its surface, so that the entire subtree properly inherits opacity.
-        renderSurface->SetDrawOpacity(accumulatedDrawOpacity);
-        renderSurface->SetDrawOpacityIsAnimating(animatingOpacityToTarget);
-        animatingOpacityToTarget = false;
-        layerDrawProperties.opacity = 1;
-        layerDrawProperties.opacity_is_animating = animatingOpacityToTarget;
-        layerDrawProperties.screen_space_opacity_is_animating = animatingOpacityToScreen;
-
-        renderSurface->SetTargetSurfaceTransformsAreAnimating(animatingTransformToTarget);
-        renderSurface->SetScreenSpaceTransformsAreAnimating(animating_transform_to_screen);
-        animatingTransformToTarget = false;
-        layerDrawProperties.target_space_transform_is_animating = animatingTransformToTarget;
-        layerDrawProperties.screen_space_transform_is_animating = animating_transform_to_screen;
-
-        // Update the aggregate hierarchy matrix to include the transform of the
-        // newly created RenderSurfaceImpl.
-        nextHierarchyMatrix.PreconcatTransform(renderSurface->draw_transform());
-
-        // The new renderSurface here will correctly clip the entire subtree. So, we do
-        // not need to continue propagating the clipping state further down the tree. This
-        // way, we can avoid transforming clipRects from ancestor target surface space to
-        // current target surface space that could cause more w < 0 headaches.
-        subtreeShouldBeClipped = false;
-
-        if (layer->mask_layer()) {
-            DrawProperties<LayerType, RenderSurfaceType>& maskLayerDrawProperties = layer->mask_layer()->draw_properties();
-            maskLayerDrawProperties.render_target = layer;
-            maskLayerDrawProperties.visible_content_rect = gfx::Rect(gfx::Point(), layer->content_bounds());
-        }
-
-        if (layer->replica_layer() && layer->replica_layer()->mask_layer()) {
-            DrawProperties<LayerType, RenderSurfaceType>& replicaMaskDrawProperties = layer->replica_layer()->mask_layer()->draw_properties();
-            replicaMaskDrawProperties.render_target = layer;
-            replicaMaskDrawProperties.visible_content_rect = gfx::Rect(gfx::Point(), layer->content_bounds());
-        }
-
-        // FIXME:  make this smarter for the SkImageFilter case (check for
-        //         pixel-moving filters)
-        if (layer->filters().hasFilterThatMovesPixels() || layer->filter())
-            nearestAncestorThatMovesPixels = renderSurface;
-
-        // The render surface clipRect is expressed in the space where this surface draws, i.e. the same space as clipRectFromAncestor.
-        renderSurface->SetIsClipped(ancestorClipsSubtree);
-        if (ancestorClipsSubtree) {
-            renderSurface->SetClipRect(clipRectFromAncestor);
-
-            gfx::Transform inverseSurfaceDrawTransform(gfx::Transform::kSkipInitialization);
-            if (!renderSurface->draw_transform().GetInverse(&inverseSurfaceDrawTransform)) {
-                // TODO(shawnsingh): Either we need to handle uninvertible transforms
-                // here, or DCHECK that the transform is invertible.
-            }
-            clipRectForSubtreeInDescendantSpace = gfx::ToEnclosingRect(MathUtil::ProjectClippedRect(inverseSurfaceDrawTransform, renderSurface->clip_rect()));
-        } else {
-            renderSurface->SetClipRect(gfx::Rect());
-            clipRectForSubtreeInDescendantSpace = clipRectFromAncestorInDescendantSpace;
-        }
-
-        renderSurface->SetNearestAncestorThatMovesPixels(nearestAncestorThatMovesPixels);
-
-        // If the new render surface is drawn translucent or with a non-integral translation
-        // then the subtree that gets drawn on this render surface cannot use LCD text.
-        subtreeCanUseLCDText = layerCanUseLCDText;
-
-        renderSurfaceLayerList.push_back(layer);
-    } else {
-        DCHECK(layer->parent());
-
-        // Note: layerDrawProperties.target_space_transform is computed above,
-        // before this if-else statement.
-        layerDrawProperties.target_space_transform_is_animating = animatingTransformToTarget;
-        layerDrawProperties.screen_space_transform_is_animating = animating_transform_to_screen;
-        layerDrawProperties.opacity = accumulatedDrawOpacity;
-        layerDrawProperties.opacity_is_animating = animatingOpacityToTarget;
-        layerDrawProperties.screen_space_opacity_is_animating = animatingOpacityToScreen;
-        sublayerMatrix = combinedTransform;
-
-        layer->ClearRenderSurface();
-
-        // Layers without renderSurfaces directly inherit the ancestor's clip status.
-        subtreeShouldBeClipped = ancestorClipsSubtree;
-        if (ancestorClipsSubtree)
-            clipRectForSubtree = clipRectFromAncestor;
-
-        // The surface's cached clipRect value propagates regardless of what clipping goes on between layers here.
-        clipRectForSubtreeInDescendantSpace = clipRectFromAncestorInDescendantSpace;
-
-        // Layers that are not their own renderTarget will render into the target of their nearest ancestor.
-        layerDrawProperties.render_target = layer->parent()->render_target();
-    }
-
-    if (adjustTextAA)
-        layerDrawProperties.can_use_lcd_text = layerCanUseLCDText;
-
-    gfx::Rect rectInTargetSpace = ToEnclosingRect(MathUtil::MapClippedRect(layer->draw_transform(), contentRect));
-
-    if (layerClipsSubtree(layer)) {
-        subtreeShouldBeClipped = true;
-        if (ancestorClipsSubtree && !layer->render_surface()) {
-            clipRectForSubtree = clipRectFromAncestor;
-            clipRectForSubtree.Intersect(rectInTargetSpace);
-        } else
-            clipRectForSubtree = rectInTargetSpace;
-    }
-
-    // Flatten to 2D if the layer doesn't preserve 3D.
-    if (!layer->preserves_3d())
-        sublayerMatrix.FlattenTo2d();
-
-    // Apply the sublayer transform at the anchor point of the layer.
-    if (!layer->sublayer_transform().IsIdentity()) {
-        sublayerMatrix.Translate(layer->anchor_point().x() * bounds.width(), layer->anchor_point().y() * bounds.height());
-        sublayerMatrix.PreconcatTransform(layer->sublayer_transform());
-        sublayerMatrix.Translate(-layer->anchor_point().x() * bounds.width(), -layer->anchor_point().y() * bounds.height());
-    }
-
-    LayerList& descendants = (layer->render_surface() ? layer->render_surface()->layer_list() : layerList);
-
-    // Any layers that are appended after this point are in the layer's subtree and should be included in the sorting process.
-    unsigned sortingStartIndex = descendants.size();
-
-    if (!layerShouldBeSkipped(layer))
-        descendants.push_back(layer);
-
-    gfx::Transform nextScrollCompensationMatrix = computeScrollCompensationMatrixForChildren(layer, parentMatrix, currentScrollCompensationMatrix);;
-
-    gfx::Rect accumulatedDrawableContentRectOfChildren;
-    for (size_t i = 0; i < layer->children().size(); ++i) {
-        LayerType* child = LayerTreeHostCommon::getChildAsRawPtr(layer->children(), i);
-        gfx::Rect drawableContentRectOfChildSubtree;
-        calculateDrawPropertiesInternal<LayerType, LayerList, RenderSurfaceType>(child, sublayerMatrix, nextHierarchyMatrix, nextScrollCompensationMatrix,
-                                                                                 clipRectForSubtree, clipRectForSubtreeInDescendantSpace, subtreeShouldBeClipped, nearestAncestorThatMovesPixels,
-                                                                                 renderSurfaceLayerList, descendants, layerSorter, maxTextureSize, deviceScaleFactor, pageScaleFactor,
-                                                                                 subtreeCanUseLCDText, drawableContentRectOfChildSubtree, updateTilePriorities);
-        if (!drawableContentRectOfChildSubtree.IsEmpty()) {
-            accumulatedDrawableContentRectOfChildren.Union(drawableContentRectOfChildSubtree);
-            if (child->render_surface())
-                descendants.push_back(child);
-        }
-    }
-
-    if (layer->render_surface() && !isRootLayer(layer) && !layer->render_surface()->layer_list().size()) {
-        removeSurfaceForEarlyExit(layer, renderSurfaceLayerList);
-        return;
-    }
-    
-    // Compute the total drawableContentRect for this subtree (the rect is in targetSurface space)
-    gfx::Rect localDrawableContentRectOfSubtree = accumulatedDrawableContentRectOfChildren;
-    if (layer->DrawsContent())
-        localDrawableContentRectOfSubtree.Union(rectInTargetSpace);
-    if (subtreeShouldBeClipped)
-        localDrawableContentRectOfSubtree.Intersect(clipRectForSubtree);
-
-    // Compute the layer's drawable content rect (the rect is in targetSurface space)
-    layerDrawProperties.drawable_content_rect = rectInTargetSpace;
-    if (subtreeShouldBeClipped)
-        layerDrawProperties.drawable_content_rect.Intersect(clipRectForSubtree);
-
-    // Tell the layer the rect that is clipped by. In theory we could use a
-    // tighter clipRect here (drawableContentRect), but that actually does not
-    // reduce how much would be drawn, and instead it would create unnecessary
-    // changes to scissor state affecting GPU performance.
-    layerDrawProperties.is_clipped = subtreeShouldBeClipped;
-    if (subtreeShouldBeClipped)
-        layerDrawProperties.clip_rect = clipRectForSubtree;
-    else {
-        // Initialize the clipRect to a safe value that will not clip the
-        // layer, just in case clipping is still accidentally used.
-        layerDrawProperties.clip_rect = rectInTargetSpace;
-    }
-
-    // Compute the layer's visible content rect (the rect is in content space)
-    layerDrawProperties.visible_content_rect = calculateVisibleContentRect(layer, clipRectForSubtreeInDescendantSpace, rectInTargetSpace);
-
-    // Compute the remaining properties for the render surface, if the layer has one.
-    if (isRootLayer(layer)) {
-        // The root layer's surface's contentRect is always the entire viewport.
-        DCHECK(layer->render_surface());
-        layer->render_surface()->SetContentRect(clipRectFromAncestor);
-    } else if (layer->render_surface() && !isRootLayer(layer)) {
-        RenderSurfaceType* renderSurface = layer->render_surface();
-        gfx::Rect clippedContentRect = localDrawableContentRectOfSubtree;
-
-        // Don't clip if the layer is reflected as the reflection shouldn't be
-        // clipped. If the layer is animating, then the surface's transform to
-        // its target is not known on the main thread, and we should not use it
-        // to clip.
-        if (!layer->replica_layer() && transformToParentIsKnown(layer)) {
-            // Note, it is correct to use ancestorClipsSubtree here, because we are looking at this layer's renderSurface, not the layer itself.
-            if (ancestorClipsSubtree && !clippedContentRect.IsEmpty()) {
-                gfx::Rect surfaceClipRect = LayerTreeHostCommon::calculateVisibleRect(renderSurface->clip_rect(), clippedContentRect, renderSurface->draw_transform());
-                clippedContentRect.Intersect(surfaceClipRect);
-            }
-        }
-
-        // The RenderSurfaceImpl backing texture cannot exceed the maximum supported
-        // texture size.
-        clippedContentRect.set_width(std::min(clippedContentRect.width(), maxTextureSize));
-        clippedContentRect.set_height(std::min(clippedContentRect.height(), maxTextureSize));
-
-        if (clippedContentRect.IsEmpty()) {
-            renderSurface->ClearLayerLists();
-            removeSurfaceForEarlyExit(layer, renderSurfaceLayerList);
-            return;
-        }
-        
-        renderSurface->SetContentRect(clippedContentRect);
-
-        // The owning layer's screenSpaceTransform has a scale from content to layer space which we need to undo and
-        // replace with a scale from the surface's subtree into layer space.
-        gfx::Transform screenSpaceTransform = layer->screen_space_transform();
-        screenSpaceTransform.Scale(layer->contents_scale_x() / renderSurfaceSublayerScale.x(), layer->contents_scale_y() / renderSurfaceSublayerScale.y());
-        renderSurface->SetScreenSpaceTransform(screenSpaceTransform);
-
-        if (layer->replica_layer()) {
-            gfx::Transform surfaceOriginToReplicaOriginTransform;
-            surfaceOriginToReplicaOriginTransform.Scale(renderSurfaceSublayerScale.x(), renderSurfaceSublayerScale.y());
-            surfaceOriginToReplicaOriginTransform.Translate(layer->replica_layer()->position().x() + layer->replica_layer()->anchor_point().x() * bounds.width(),
-                                                            layer->replica_layer()->position().y() + layer->replica_layer()->anchor_point().y() * bounds.height());
-            surfaceOriginToReplicaOriginTransform.PreconcatTransform(layer->replica_layer()->transform());
-            surfaceOriginToReplicaOriginTransform.Translate(-layer->replica_layer()->anchor_point().x() * bounds.width(), -layer->replica_layer()->anchor_point().y() * bounds.height());
-            surfaceOriginToReplicaOriginTransform.Scale(1 / renderSurfaceSublayerScale.x(), 1 / renderSurfaceSublayerScale.y());
-
-            // Compute the replica's "originTransform" that maps from the replica's origin space to the target surface origin space.
-            gfx::Transform replicaOriginTransform = layer->render_surface()->draw_transform() * surfaceOriginToReplicaOriginTransform;
-            renderSurface->SetReplicaDrawTransform(replicaOriginTransform);
-
-            // Compute the replica's "screenSpaceTransform" that maps from the replica's origin space to the screen's origin space.
-            gfx::Transform replicaScreenSpaceTransform = layer->render_surface()->screen_space_transform() * surfaceOriginToReplicaOriginTransform;
-            renderSurface->SetReplicaScreenSpaceTransform(replicaScreenSpaceTransform);
-        }
-    }
-
-    if (updateTilePriorities)
-        updateTilePrioritiesForLayer(layer);
-
-    // If neither this layer nor any of its children were added, early out.
-    if (sortingStartIndex == descendants.size())
-        return;
-
-    // If preserves-3d then sort all the descendants in 3D so that they can be
-    // drawn from back to front. If the preserves-3d property is also set on the parent then
-    // skip the sorting as the parent will sort all the descendants anyway.
-    if (layerSorter && descendants.size() && layer->preserves_3d() && (!layer->parent() || !layer->parent()->preserves_3d()))
-        sortLayers(descendants.begin() + sortingStartIndex, descendants.end(), layerSorter);
-
-    if (layer->render_surface())
-        drawableContentRectOfSubtree = gfx::ToEnclosingRect(layer->render_surface()->DrawableContentRect());
-    else
-        drawableContentRectOfSubtree = localDrawableContentRectOfSubtree;
-
-    if (layer->HasContributingDelegatedRenderPasses())
-        layer->render_target()->render_surface()->AddContributingDelegatedRenderPassLayer(layer);
-}
-
-void LayerTreeHostCommon::calculateDrawProperties(Layer* rootLayer, const gfx::Size& deviceViewportSize, float deviceScaleFactor, float pageScaleFactor, int maxTextureSize, bool canUseLCDText, std::vector<scoped_refptr<Layer> >& renderSurfaceLayerList)
-{
-    gfx::Rect totalDrawableContentRect;
-    gfx::Transform identityMatrix;
-    gfx::Transform deviceScaleTransform;
-    deviceScaleTransform.Scale(deviceScaleFactor, deviceScaleFactor);
-    std::vector<scoped_refptr<Layer> > dummyLayerList;
-
-    // The root layer's renderSurface should receive the deviceViewport as the initial clipRect.
-    bool subtreeShouldBeClipped = true;
-    gfx::Rect deviceViewportRect(gfx::Point(), deviceViewportSize);
-    bool updateTilePriorities = false;
-
-    // This function should have received a root layer.
-    DCHECK(isRootLayer(rootLayer));
-
-    preCalculateMetaInformation<Layer>(rootLayer);
-    calculateDrawPropertiesInternal<Layer, std::vector<scoped_refptr<Layer> >, RenderSurface>(
-        rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
-        deviceViewportRect, deviceViewportRect, subtreeShouldBeClipped, 0, renderSurfaceLayerList,
-        dummyLayerList, 0, maxTextureSize,
-        deviceScaleFactor, pageScaleFactor, canUseLCDText, totalDrawableContentRect,
-        updateTilePriorities);
-
-    // The dummy layer list should not have been used.
-    DCHECK(dummyLayerList.size() == 0);
-    // A root layer renderSurface should always exist after calculateDrawProperties.
-    DCHECK(rootLayer->render_surface());
-}
-
-void LayerTreeHostCommon::calculateDrawProperties(LayerImpl* rootLayer, const gfx::Size& deviceViewportSize, float deviceScaleFactor, float pageScaleFactor, int maxTextureSize, bool canUseLCDText, std::vector<LayerImpl*>& renderSurfaceLayerList, bool updateTilePriorities)
-{
-    gfx::Rect totalDrawableContentRect;
-    gfx::Transform identityMatrix;
-    gfx::Transform deviceScaleTransform;
-    deviceScaleTransform.Scale(deviceScaleFactor, deviceScaleFactor);
-    std::vector<LayerImpl*> dummyLayerList;
-    LayerSorter layerSorter;
-    
-    // The root layer's renderSurface should receive the deviceViewport as the initial clipRect.
-    bool subtreeShouldBeClipped = true;
-    gfx::Rect deviceViewportRect(gfx::Point(), deviceViewportSize);
-
-    // This function should have received a root layer.
-    DCHECK(isRootLayer(rootLayer));
-
-    preCalculateMetaInformation<LayerImpl>(rootLayer);
-    calculateDrawPropertiesInternal<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl>(
-        rootLayer, deviceScaleTransform, identityMatrix, identityMatrix,
-        deviceViewportRect, deviceViewportRect, subtreeShouldBeClipped, 0, renderSurfaceLayerList,
-        dummyLayerList, &layerSorter, maxTextureSize,
-        deviceScaleFactor, pageScaleFactor, canUseLCDText, totalDrawableContentRect,
-        updateTilePriorities);
-
-    // The dummy layer list should not have been used.
-    DCHECK(dummyLayerList.size() == 0);
-    // A root layer renderSurface should always exist after calculateDrawProperties.
-    DCHECK(rootLayer->render_surface());
-}
-
-static bool pointHitsRect(const gfx::PointF& screenSpacePoint, const gfx::Transform& localSpaceToScreenSpaceTransform, gfx::RectF localSpaceRect)
-{
-    // If the transform is not invertible, then assume that this point doesn't hit this rect.
-    gfx::Transform inverseLocalSpaceToScreenSpace(gfx::Transform::kSkipInitialization);
-    if (!localSpaceToScreenSpaceTransform.GetInverse(&inverseLocalSpaceToScreenSpace))
-        return false;
-
-    // Transform the hit test point from screen space to the local space of the given rect.
-    bool clipped = false;
-    gfx::PointF hitTestPointInLocalSpace = MathUtil::ProjectPoint(inverseLocalSpaceToScreenSpace, screenSpacePoint, &clipped);
-
-    // If projectPoint could not project to a valid value, then we assume that this point doesn't hit this rect.
-    if (clipped)
-        return false;
-
-    return localSpaceRect.Contains(hitTestPointInLocalSpace);
-}
-
-static bool pointHitsRegion(gfx::PointF screenSpacePoint, const gfx::Transform& screenSpaceTransform, const Region& layerSpaceRegion, float layerContentScaleX, float layerContentScaleY)
-{
-    // If the transform is not invertible, then assume that this point doesn't hit this region.
-    gfx::Transform inverseScreenSpaceTransform(gfx::Transform::kSkipInitialization);
-    if (!screenSpaceTransform.GetInverse(&inverseScreenSpaceTransform))
-        return false;
-
-    // Transform the hit test point from screen space to the local space of the given region.
-    bool clipped = false;
-    gfx::PointF hitTestPointInContentSpace = MathUtil::ProjectPoint(inverseScreenSpaceTransform, screenSpacePoint, &clipped);
-    gfx::PointF hitTestPointInLayerSpace = gfx::ScalePoint(hitTestPointInContentSpace, 1 / layerContentScaleX, 1 / layerContentScaleY);
-
-    // If projectPoint could not project to a valid value, then we assume that this point doesn't hit this region.
-    if (clipped)
-        return false;
-
-    return layerSpaceRegion.Contains(gfx::ToRoundedPoint(hitTestPointInLayerSpace));
-}
-
-static bool pointIsClippedBySurfaceOrClipRect(const gfx::PointF& screenSpacePoint, LayerImpl* layer)
-{
-    LayerImpl* current_layer = layer;
-
-    // Walk up the layer tree and hit-test any renderSurfaces and any layer clipRects that are active.
-    while (current_layer) {
-        if (current_layer->render_surface() && !pointHitsRect(screenSpacePoint, current_layer->render_surface()->screen_space_transform(), current_layer->render_surface()->content_rect()))
-            return true;
-
-        // Note that drawableContentRects are actually in targetSurface space, so the transform we
-        // have to provide is the target surface's screenSpaceTransform.
-        LayerImpl* renderTarget = current_layer->render_target();
-        if (layerClipsSubtree(current_layer) && !pointHitsRect(screenSpacePoint, renderTarget->render_surface()->screen_space_transform(), current_layer->drawable_content_rect()))
-            return true;
-
-        current_layer = current_layer->parent();
-    }
-
-    // If we have finished walking all ancestors without having already exited, then the point is not clipped by any ancestors.
+  }
+
+  if (update_tile_priorities)
+    UpdateTilePrioritiesForLayer(layer);
+
+  // If neither this layer nor any of its children were added, early out.
+  if (sorting_start_index == descendants.size())
+    return;
+
+  // If preserves-3d then sort all the descendants in 3D so that they can be
+  // drawn from back to front. If the preserves-3d property is also set on the
+  // parent then skip the sorting as the parent will sort all the descendants
+  // anyway.
+  if (layer_sorter && descendants.size() && layer->preserves_3d() &&
+      (!layer->parent() || !layer->parent()->preserves_3d())) {
+    SortLayers(descendants.begin() + sorting_start_index,
+               descendants.end(),
+               layer_sorter);
+  }
+
+  if (layer->render_surface()) {
+    *drawable_content_rect_of_subtree =
+        gfx::ToEnclosingRect(layer->render_surface()->DrawableContentRect());
+  } else {
+    *drawable_content_rect_of_subtree = local_drawable_content_rect_of_subtree;
+  }
+
+  if (layer->HasContributingDelegatedRenderPasses()) {
+    layer->render_target()->render_surface()->
+        AddContributingDelegatedRenderPassLayer(layer);
+  }
+}
+
+void LayerTreeHostCommon::CalculateDrawProperties(
+    Layer* root_layer,
+    gfx::Size device_viewport_size,
+    float device_scale_factor,
+    float page_scale_factor,
+    int max_texture_size,
+    bool can_use_lcd_text,
+    std::vector<scoped_refptr<Layer> >* render_surface_layer_list) {
+  gfx::Rect total_drawable_content_rect;
+  gfx::Transform identity_matrix;
+  gfx::Transform device_scale_transform;
+  device_scale_transform.Scale(device_scale_factor, device_scale_factor);
+  std::vector<scoped_refptr<Layer> > dummy_layer_list;
+
+  // The root layer's render_surface should receive the deviceViewport as the
+  // initial clipRect.
+  bool subtree_should_be_clipped = true;
+  gfx::Rect device_viewport_rect(gfx::Point(), device_viewport_size);
+  bool update_tile_priorities = false;
+
+  // This function should have received a root layer.
+  DCHECK(IsRootLayer(root_layer));
+
+  PreCalculateMetaInformation<Layer>(root_layer);
+  CalculateDrawPropertiesInternal<Layer,
+                                  std::vector<scoped_refptr<Layer> >,
+                                  RenderSurface>(root_layer,
+                                                 device_scale_transform,
+                                                 identity_matrix,
+                                                 identity_matrix,
+                                                 device_viewport_rect,
+                                                 device_viewport_rect,
+                                                 subtree_should_be_clipped,
+                                                 NULL,
+                                                 render_surface_layer_list,
+                                                 &dummy_layer_list,
+                                                 NULL,
+                                                 max_texture_size,
+                                                 device_scale_factor,
+                                                 page_scale_factor,
+                                                 can_use_lcd_text,
+                                                 &total_drawable_content_rect,
+                                                 update_tile_priorities);
+
+  // The dummy layer list should not have been used.
+  DCHECK_EQ(dummy_layer_list.size(), 0);
+  // A root layer render_surface should always exist after
+  // calculateDrawProperties.
+  DCHECK(root_layer->render_surface());
+}
+
+void LayerTreeHostCommon::CalculateDrawProperties(
+    LayerImpl* root_layer,
+    gfx::Size device_viewport_size,
+    float device_scale_factor,
+    float page_scale_factor,
+    int max_texture_size,
+    bool can_use_lcd_text,
+    std::vector<LayerImpl*>* render_surface_layer_list,
+    bool update_tile_priorities) {
+  gfx::Rect total_drawable_content_rect;
+  gfx::Transform identity_matrix;
+  gfx::Transform device_scale_transform;
+  device_scale_transform.Scale(device_scale_factor, device_scale_factor);
+  std::vector<LayerImpl*> dummy_layer_list;
+  LayerSorter layer_sorter;
+
+  // The root layer's render_surface should receive the deviceViewport as the
+  // initial clipRect.
+  bool subtree_should_be_clipped = true;
+  gfx::Rect device_viewport_rect(gfx::Point(), device_viewport_size);
+
+  // This function should have received a root layer.
+  DCHECK(IsRootLayer(root_layer));
+
+  PreCalculateMetaInformation<LayerImpl>(root_layer);
+  CalculateDrawPropertiesInternal<LayerImpl,
+                                  std::vector<LayerImpl*>,
+                                  RenderSurfaceImpl>(
+      root_layer,
+      device_scale_transform,
+      identity_matrix,
+      identity_matrix,
+      device_viewport_rect,
+      device_viewport_rect,
+      subtree_should_be_clipped,
+      NULL,
+      render_surface_layer_list,
+      &dummy_layer_list,
+      &layer_sorter,
+      max_texture_size,
+      device_scale_factor,
+      page_scale_factor,
+      can_use_lcd_text,
+      &total_drawable_content_rect,
+      update_tile_priorities);
+
+  // The dummy layer list should not have been used.
+  DCHECK_EQ(dummy_layer_list.size(), 0);
+  // A root layer render_surface should always exist after
+  // calculateDrawProperties.
+  DCHECK(root_layer->render_surface());
+}
+
+static bool PointHitsRect(
+    gfx::PointF screen_space_point,
+    const gfx::Transform& local_space_to_screen_space_transform,
+    gfx::RectF local_space_rect) {
+  // If the transform is not invertible, then assume that this point doesn't hit
+  // this rect.
+  gfx::Transform inverse_local_space_to_screen_space(
+      gfx::Transform::kSkipInitialization);
+  if (!local_space_to_screen_space_transform.GetInverse(
+          &inverse_local_space_to_screen_space))
     return false;
-}
-
-LayerImpl* LayerTreeHostCommon::findLayerThatIsHitByPoint(const gfx::PointF& screenSpacePoint, const std::vector<LayerImpl*>& renderSurfaceLayerList)
-{
-    LayerImpl* foundLayer = 0;
-
-    typedef LayerIterator<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl, LayerIteratorActions::FrontToBack> LayerIteratorType;
-    LayerIteratorType end = LayerIteratorType::End(&renderSurfaceLayerList);
-
-    for (LayerIteratorType it = LayerIteratorType::Begin(&renderSurfaceLayerList); it != end; ++it) {
-        // We don't want to consider renderSurfaces for hit testing.
-        if (!it.represents_itself())
-            continue;
-
-        LayerImpl* current_layer = (*it);
-
-        gfx::RectF contentRect(gfx::PointF(), current_layer->content_bounds());
-        if (!pointHitsRect(screenSpacePoint, current_layer->screen_space_transform(), contentRect))
-            continue;
-
-        // At this point, we think the point does hit the layer, but we need to walk up
-        // the parents to ensure that the layer was not clipped in such a way that the
-        // hit point actually should not hit the layer.
-        if (pointIsClippedBySurfaceOrClipRect(screenSpacePoint, current_layer))
-            continue;
-
-        // Skip the HUD layer.
-        if (current_layer == current_layer->layer_tree_impl()->hud_layer())
-            continue;
-
-        foundLayer = current_layer;
-        break;
-    }
-
-    // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
-    return foundLayer;
-}
-
-LayerImpl* LayerTreeHostCommon::findLayerThatIsHitByPointInTouchHandlerRegion(const gfx::PointF& screenSpacePoint, const std::vector<LayerImpl*>& renderSurfaceLayerList)
-{
-    LayerImpl* foundLayer = 0;
-
-    typedef LayerIterator<LayerImpl, std::vector<LayerImpl*>, RenderSurfaceImpl, LayerIteratorActions::FrontToBack> LayerIteratorType;
-    LayerIteratorType end = LayerIteratorType::End(&renderSurfaceLayerList);
-
-    for (LayerIteratorType it = LayerIteratorType::Begin(&renderSurfaceLayerList); it != end; ++it) {
-        // We don't want to consider renderSurfaces for hit testing.
-        if (!it.represents_itself())
-            continue;
-
-        LayerImpl* current_layer = (*it);
-
-        if (!layerHasTouchEventHandlersAt(screenSpacePoint, current_layer))
-            continue;
-
-        foundLayer = current_layer;
-        break;
-    }
-
-    // This can potentially return 0, which means the screenSpacePoint did not successfully hit test any layers, not even the root layer.
-    return foundLayer;
-}
-
-bool LayerTreeHostCommon::layerHasTouchEventHandlersAt(const gfx::PointF& screenSpacePoint, LayerImpl* layerImpl) {
-  if (layerImpl->touch_event_handler_region().IsEmpty())
-      return false;
-
-  if (!pointHitsRegion(screenSpacePoint, layerImpl->screen_space_transform(), layerImpl->touch_event_handler_region(), layerImpl->contents_scale_x(), layerImpl->contents_scale_y()))
-     return false;;
-
-  // At this point, we think the point does hit the touch event handler region on the layer, but we need to walk up
-  // the parents to ensure that the layer was not clipped in such a way that the
-  // hit point actually should not hit the layer.
-  if (pointIsClippedBySurfaceOrClipRect(screenSpacePoint, layerImpl))
-     return false;
+
+  // Transform the hit test point from screen space to the local space of the
+  // given rect.
+  bool clipped = false;
+  gfx::PointF hit_test_point_in_local_space = MathUtil::ProjectPoint(
+      inverse_local_space_to_screen_space, screen_space_point, &clipped);
+
+  // If ProjectPoint could not project to a valid value, then we assume that
+  // this point doesn't hit this rect.
+  if (clipped)
+    return false;
+
+  return local_space_rect.Contains(hit_test_point_in_local_space);
+}
+
+static bool PointHitsRegion(gfx::PointF screen_space_point,
+                            const gfx::Transform& screen_space_transform,
+                            const Region& layer_space_region,
+                            float layer_content_scale_x,
+                            float layer_content_scale_y) {
+  // If the transform is not invertible, then assume that this point doesn't hit
+  // this region.
+  gfx::Transform inverse_screen_space_transform(
+      gfx::Transform::kSkipInitialization);
+  if (!screen_space_transform.GetInverse(&inverse_screen_space_transform))
+    return false;
+
+  // Transform the hit test point from screen space to the local space of the
+  // given region.
+  bool clipped = false;
+  gfx::PointF hit_test_point_in_content_space = MathUtil::ProjectPoint(
+      inverse_screen_space_transform, screen_space_point, &clipped);
+  gfx::PointF hit_test_point_in_layer_space =
+      gfx::ScalePoint(hit_test_point_in_content_space,
+                      1.f / layer_content_scale_x,
+                      1.f / layer_content_scale_y);
+
+  // If ProjectPoint could not project to a valid value, then we assume that
+  // this point doesn't hit this region.
+  if (clipped)
+    return false;
+
+  return layer_space_region.Contains(
+      gfx::ToRoundedPoint(hit_test_point_in_layer_space));
+}
+
+static bool PointIsClippedBySurfaceOrClipRect(gfx::PointF screen_space_point,
+                                              LayerImpl* layer) {
+  LayerImpl* current_layer = layer;
+
+  // Walk up the layer tree and hit-test any render_surfaces and any layer
+  // clip rects that are active.
+  while (current_layer) {
+    if (current_layer->render_surface() &&
+        !PointHitsRect(
+            screen_space_point,
+            current_layer->render_surface()->screen_space_transform(),
+            current_layer->render_surface()->content_rect()))
+      return true;
+
+    // Note that drawable content rects are actually in target surface space, so
+    // the transform we have to provide is the target surface's
+    // screen_space_transform.
+    LayerImpl* render_target = current_layer->render_target();
+    if (LayerClipsSubtree(current_layer) &&
+        !PointHitsRect(
+            screen_space_point,
+            render_target->render_surface()->screen_space_transform(),
+            current_layer->drawable_content_rect()))
+      return true;
+
+    current_layer = current_layer->parent();
+  }
+
+  // If we have finished walking all ancestors without having already exited,
+  // then the point is not clipped by any ancestors.
+  return false;
+}
+
+LayerImpl* LayerTreeHostCommon::FindLayerThatIsHitByPoint(
+    gfx::PointF screen_space_point,
+    const std::vector<LayerImpl*>& render_surface_layer_list) {
+  LayerImpl* found_layer = NULL;
+
+  typedef LayerIterator<LayerImpl,
+                        std::vector<LayerImpl*>,
+                        RenderSurfaceImpl,
+                        LayerIteratorActions::FrontToBack> LayerIteratorType;
+  LayerIteratorType end = LayerIteratorType::End(&render_surface_layer_list);
+
+  for (LayerIteratorType
+           it = LayerIteratorType::Begin(&render_surface_layer_list);
+       it != end;
+       ++it) {
+    // We don't want to consider render_surfaces for hit testing.
+    if (!it.represents_itself())
+      continue;
+
+    LayerImpl* current_layer = (*it);
+
+    gfx::RectF content_rect(gfx::PointF(), current_layer->content_bounds());
+    if (!PointHitsRect(screen_space_point,
+                       current_layer->screen_space_transform(),
+                       content_rect))
+      continue;
+
+    // At this point, we think the point does hit the layer, but we need to walk
+    // up the parents to ensure that the layer was not clipped in such a way
+    // that the hit point actually should not hit the layer.
+    if (PointIsClippedBySurfaceOrClipRect(screen_space_point, current_layer))
+      continue;
+
+    // Skip the HUD layer.
+    if (current_layer == current_layer->layer_tree_impl()->hud_layer())
+      continue;
+
+    found_layer = current_layer;
+    break;
+  }
+
+  // This can potentially return NULL, which means the screen_space_point did
+  // not successfully hit test any layers, not even the root layer.
+  return found_layer;
+}
+
+LayerImpl* LayerTreeHostCommon::FindLayerThatIsHitByPointInTouchHandlerRegion(
+    gfx::PointF screen_space_point,
+    const std::vector<LayerImpl*>& render_surface_layer_list) {
+  LayerImpl* found_layer = NULL;
+
+  typedef LayerIterator<LayerImpl,
+                        std::vector<LayerImpl*>,
+                        RenderSurfaceImpl,
+                        LayerIteratorActions::FrontToBack> LayerIteratorType;
+  LayerIteratorType end = LayerIteratorType::End(&render_surface_layer_list);
+
+  for (LayerIteratorType
+           it = LayerIteratorType::Begin(&render_surface_layer_list);
+       it != end;
+       ++it) {
+    // We don't want to consider render_surfaces for hit testing.
+    if (!it.represents_itself())
+      continue;
+
+    LayerImpl* current_layer = (*it);
+
+    if (!LayerHasTouchEventHandlersAt(screen_space_point, current_layer))
+      continue;
+
+    found_layer = current_layer;
+    break;
+  }
+
+  // This can potentially return NULL, which means the screen_space_point did
+  // not successfully hit test any layers, not even the root layer.
+  return found_layer;
+}
+
+bool LayerTreeHostCommon::LayerHasTouchEventHandlersAt(
+    gfx::PointF screen_space_point,
+    LayerImpl* layer_impl) {
+  if (layer_impl->touch_event_handler_region().IsEmpty())
+    return false;
+
+  if (!PointHitsRegion(screen_space_point,
+                       layer_impl->screen_space_transform(),
+                       layer_impl->touch_event_handler_region(),
+                       layer_impl->contents_scale_x(),
+                       layer_impl->contents_scale_y()))
+    return false;
+
+  // At this point, we think the point does hit the touch event handler region
+  // on the layer, but we need to walk up the parents to ensure that the layer
+  // was not clipped in such a way that the hit point actually should not hit
+  // the layer.
+  if (PointIsClippedBySurfaceOrClipRect(screen_space_point, layer_impl))
+    return false;
 
   return true;
 }
 }  // namespace cc