Add a |scope| argument to TRACE_EVENT_INSTANT* and require its presence.

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"
@@ skipping 280 matching lines @@
 
   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");
+        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface flattening",
+        TRACE_EVENT_SCOPE_THREAD);
     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");
+        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface clipping",
+        TRACE_EVENT_SCOPE_THREAD);
     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");
+        "LayerTreeHostCommon::SubtreeShouldRenderToSeparateSurface opacity",
+        TRACE_EVENT_SCOPE_THREAD);
     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
@@ skipping 1233 matching lines @@
   // 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