cc: Compute mask draw properties directly

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 1072 matching lines @@
         clip_node->data.layers_are_clipped_when_surfaces_disabled;
   }
 
   gfx::Rect bounds_in_target_space = MathUtil::MapEnclosingClippedRect(
       layer->draw_properties().target_space_transform,
       gfx::Rect(layer->bounds()));
   layer->draw_properties().drawable_content_rect = LayerDrawableContentRect(
       layer, bounds_in_target_space, layer->draw_properties().clip_rect);
 }
 
+void ComputeMaskDrawProperties(LayerImpl* mask_layer,
+                               const PropertyTrees* property_trees) {
+  // Mask draw properties are used only for rastering, so most of the draw
+  // properties computed for other layers are not needed.
+  mask_layer->draw_properties().screen_space_transform =
+      ScreenSpaceTransformInternal(mask_layer,
+                                   property_trees->transform_tree.Node(
+                                       mask_layer->transform_tree_index()));
+  mask_layer->draw_properties().visible_layer_rect =
+      gfx::Rect(mask_layer->bounds());

[ajuma, 2016/06/07 17:59:39]

We were previously using the owning layer's bounds as the visible rect
(regardless of what's actually visible). Using the mask layer's own bounds seems
to make more sense. Masks are rastered as a single tile, so the only thing that
seems to matter for the visible rect is empty vs non-empty.

+}
+
 void ComputeSurfaceDrawProperties(const PropertyTrees* property_trees,
                                   RenderSurfaceImpl* render_surface) {
   const ClipNode* clip_node =
       property_trees->clip_tree.Node(render_surface->ClipTreeIndex());
 
   SetSurfaceIsClipped(clip_node, render_surface);
   SetSurfaceDrawOpacity(property_trees->effect_tree, render_surface);
   SetSurfaceDrawTransform(property_trees->transform_tree, render_surface);
   render_surface->SetScreenSpaceTransform(
       property_trees->transform_tree.ToScreenSpaceTransformWithoutSublayerScale(
@@ skipping 111 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