Roll Chrome into Mojo.

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 190 matching lines @@
   virtual void DidDraw(ResourceProvider* resource_provider);
 
   virtual void GetContentsResourceId(ResourceProvider::ResourceId* resource_id,
                                      gfx::Size* resource_size) const;
 
   virtual bool HasDelegatedContent() const;
   virtual bool HasContributingDelegatedRenderPasses() const;
   virtual RenderPassId FirstContributingRenderPassId() const;
   virtual RenderPassId NextContributingRenderPassId(RenderPassId id) const;
 
-  virtual void UpdateTiles(const Occlusion& occlusion_in_layer_space,
-                           bool resourceless_software_draw) {}
+  // Updates the layer's tiles. This should return true if meaningful work was
+  // done. That is, if an early-out was hit and as a result the internal state
+  // of tiles didn't change, this function should return false.
+  virtual bool UpdateTiles(const Occlusion& occlusion_in_layer_space,
+                           bool resourceless_software_draw);
   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);
@@ skipping 493 matching lines @@
   DrawProperties<LayerImpl> draw_properties_;
 
   scoped_refptr<base::debug::ConvertableToTraceFormat> debug_info_;
   scoped_ptr<RenderSurfaceImpl> render_surface_;
   DISALLOW_COPY_AND_ASSIGN(LayerImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_LAYER_IMPL_H_