Keeping track of descendants that draw content instead of recalcualting

cc/layers/layer_impl.h

 // 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.
 
 #ifndef CC_LAYERS_LAYER_IMPL_H_
 #define CC_LAYERS_LAYER_IMPL_H_
 
 #include <set>
 #include <string>
 
@@ skipping 121 matching lines @@
   LayerImpl* scroll_parent() { return scroll_parent_; }
   const LayerImpl* scroll_parent() const { return scroll_parent_; }
 
   void SetScrollChildren(std::set<LayerImpl*>* children);
 
   std::set<LayerImpl*>* scroll_children() { return scroll_children_.get(); }
   const std::set<LayerImpl*>* scroll_children() const {
     return scroll_children_.get();
   }
 
+  void SetNumDescendantsThatDrawContent(int num_descendants);
   void SetClipParent(LayerImpl* ancestor);
 
   LayerImpl* clip_parent() {
     return clip_parent_;
   }
   const LayerImpl* clip_parent() const {
     return clip_parent_;
   }
 
   void SetClipChildren(std::set<LayerImpl*>* children);
@@ skipping 51 matching lines @@
   virtual void UpdateTiles(
       const OcclusionTracker<LayerImpl>* occlusion_tracker) {}
   virtual void NotifyTileStateChanged(const Tile* tile) {}
 
   virtual ScrollbarLayerImplBase* ToScrollbarLayer();
 
   // Returns true if this layer has content to draw.
   void SetDrawsContent(bool draws_content);
   bool DrawsContent() const { return draws_content_; }
 
+  int NumDescendantsThatDrawContent() const;
   void SetHideLayerAndSubtree(bool hide);
   bool hide_layer_and_subtree() const { return hide_layer_and_subtree_; }
 
   bool force_render_surface() const { return force_render_surface_; }
   void SetForceRenderSurface(bool force) { force_render_surface_ = force; }
 
   void SetTransformOrigin(const gfx::Point3F& transform_origin);
   gfx::Point3F transform_origin() const { return transform_origin_; }
 
   void SetBackgroundColor(SkColor background_color);
@@ skipping 420 matching lines @@
   SkXfermode::Mode blend_mode_;
   gfx::PointF position_;
   gfx::Transform transform_;
 
   LayerPositionConstraint position_constraint_;
 
   gfx::Vector2dF scroll_delta_;
   gfx::Vector2d sent_scroll_delta_;
   gfx::Vector2dF last_scroll_offset_;
 
+  int num_descendants_that_draw_content_;
+
   // The global depth value of the center of the layer. This value is used
   // to sort layers from back to front.
   float draw_depth_;
 
   FilterOperations filters_;
   FilterOperations background_filters_;
 
  protected:
   friend class TreeSynchronizer;
 
@@ skipping 37 matching lines @@
   DrawProperties<LayerImpl> draw_properties_;
 
   scoped_refptr<base::debug::ConvertableToTraceFormat> debug_info_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_