Changes subtreeShouldRenderToSeparateSurface logic to account for explicit clipping

cc/draw_properties.h

 // Copyright 2012 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.
 
 #ifndef CC_DRAW_PROPERTIES_H_
 #define CC_DRAW_PROPERTIES_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/transform.h"
 
 namespace cc {
 
 // Container for properties that layers need to compute before they can be
 // drawn.
 template<typename LayerType, typename RenderSurfaceType>
 struct CC_EXPORT DrawProperties {
     DrawProperties()
         : opacity(0)
         , opacity_is_animating(false)
         , screen_space_opacity_is_animating(false)
         , target_space_transform_is_animating(false)
         , screen_space_transform_is_animating(false)
         , can_use_lcd_text(false)
         , is_clipped(false)
         , render_target(0)
         , contents_scale_x(1)
         , contents_scale_y(1)
         , num_descendants_that_draw_content(0)
+        , descendants_can_clip_selves(false)
     {
     }
 
     // Transforms objects from content space to target surface space, where
     // this layer would be drawn.
     gfx::Transform target_space_transform;
 
     // Transforms objects from content space to screen space (viewport space).
     gfx::Transform screen_space_transform;
 
@@ skipping 40 matching lines @@
     // The scale used to move between layer space and content space, and bounds
     // of the space. One is always a function of the other, but which one
     // depends on the layer type. For picture layers, this is an ideal scale,
     // and not always the one used.
     float contents_scale_x;
     float contents_scale_y;
     gfx::Size content_bounds;
 
     // Does not include this layer itself, only its children and descendants.
     int num_descendants_that_draw_content;
+
+    // If true, every descendant in the sub-tree can clip itself without the
+    // need to use hardware sissoring or a new render target.
+    bool descendants_can_clip_selves;
 };
 
 }  // namespace cc
 
 #endif  // CC_DRAW_PROPERTIES_H_