cc: Merge the DrawLayer()/DrawFrame() and SwapBuffers() methods.

cc/trees/layer_tree_host_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_TREES_LAYER_TREE_HOST_IMPL_H_
 #define CC_TREES_LAYER_TREE_HOST_IMPL_H_
 
 #include <stddef.h>
 
 #include <bitset>
@@ skipping 291 matching lines @@
   gfx::ScrollOffset GetScrollOffsetForAnimation(
       ElementId element_id) const override;
 
   virtual bool PrepareTiles();
 
   // Returns DRAW_SUCCESS unless problems occured preparing the frame, and we
   // should try to avoid displaying the frame. If PrepareToDraw is called,
   // DidDrawAllLayers must also be called, regardless of whether DrawLayers is
   // called between the two.
   virtual DrawResult PrepareToDraw(FrameData* frame);
-  void DrawLayers(FrameData* frame);
+  virtual bool DrawLayers(FrameData* frame);
   // Must be called if and only if PrepareToDraw was called.
   void DidDrawAllLayers(const FrameData& frame);
 
   const LayerTreeSettings& settings() const { return settings_; }
 
   // Evict all textures by enforcing a memory policy with an allocation of 0.
   void EvictTexturesForTesting();
 
   // When blocking, this prevents client_->NotifyReadyToActivate() from being
   // called. When disabled, it calls client_->NotifyReadyToActivate()
@@ skipping 90 matching lines @@
 
   bool create_low_res_tiling() const {
     return settings_.create_low_res_tiling && !use_gpu_rasterization_;
   }
   ResourcePool* resource_pool() { return resource_pool_.get(); }
   DelegatingRenderer* renderer() { return renderer_.get(); }
   ImageDecodeController* image_decode_controller() {
     return image_decode_controller_.get();
   }
 
-  virtual bool SwapBuffers(const FrameData& frame);
   virtual void WillBeginImplFrame(const BeginFrameArgs& args);
   virtual void DidFinishImplFrame();
   void DidModifyTilePriorities();
 
   LayerTreeImpl* active_tree() { return active_tree_.get(); }
   const LayerTreeImpl* active_tree() const { return active_tree_.get(); }
   LayerTreeImpl* pending_tree() { return pending_tree_.get(); }
   const LayerTreeImpl* pending_tree() const { return pending_tree_.get(); }
   LayerTreeImpl* recycle_tree() { return recycle_tree_.get(); }
   const LayerTreeImpl* recycle_tree() const { return recycle_tree_.get(); }
@@ skipping 418 matching lines @@
 
   std::unique_ptr<PendingTreeDurationHistogramTimer>
       pending_tree_duration_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerTreeHostImpl);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_IMPL_H_