cc: Enable composited border-radius scrolling.

cc/trees/draw_property_utils.cc

 // Copyright 2014 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/draw_property_utils.h"
 
 #include <stddef.h>
 
 #include <vector>
 
@@ skipping 998 matching lines @@
   // TODO(sunxd): the draw transform of a mask layer misses the "scale to fit"
   // factor from mask layer to its parent. So does the screen space transform.
   // It does not cause a problem because currently we only have 1:1 mask layer.
   mask_layer->draw_properties().target_space_transform = DrawTransform(
       mask_layer, property_trees->transform_tree, property_trees->effect_tree);
   mask_layer->draw_properties().screen_space_transform =
       ScreenSpaceTransformInternal(mask_layer,
                                    property_trees->transform_tree);
   mask_layer->draw_properties().visible_layer_rect =
       gfx::Rect(mask_layer->bounds());
+  mask_layer->draw_properties().opacity =

[enne (OOO), 2017/05/15 18:01:44]

Sorry for my confusion, but I'm not sure why you need to do this.  Can you walk
me through why this is an equivalent for not skipping quads before?

+      LayerDrawOpacity(mask_layer, property_trees->effect_tree);
 }
 
 void ComputeSurfaceDrawProperties(PropertyTrees* property_trees,
                                   RenderSurfaceImpl* render_surface) {
   SetSurfaceIsClipped(property_trees->clip_tree, render_surface);
   SetSurfaceDrawOpacity(property_trees->effect_tree, render_surface);
   SetSurfaceDrawTransform(property_trees, render_surface);
   render_surface->SetScreenSpaceTransform(
       property_trees->ToScreenSpaceTransformWithoutSurfaceContentsScale(
           render_surface->TransformTreeIndex(),
@@ skipping 34 matching lines @@
 void UpdateElasticOverscroll(PropertyTrees* property_trees,
                              const Layer* overscroll_elasticity_layer,
                              const gfx::Vector2dF& elastic_overscroll) {
   UpdateElasticOverscrollInternal(property_trees, overscroll_elasticity_layer,
                                   elastic_overscroll);
 }
 
 }  // namespace draw_property_utils
 
 }  // namespace cc