cc: Don't draw and swap if the frame will not change.

cc/trees/single_thread_proxy.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_SINGLE_THREAD_PROXY_H_
 #define CC_TREES_SINGLE_THREAD_PROXY_H_
 
 #include <limits>
 
 #include "base/time.h"
@@ skipping 60 matching lines @@
   virtual void RenewTreePriority() OVERRIDE {}
   virtual void RequestScrollbarAnimationOnImplThread(base::TimeDelta delay)
       OVERRIDE {}
 
   // Called by the legacy path where RenderWidget does the scheduling.
   void CompositeImmediately(base::TimeTicks frame_begin_time);
 
  private:
   explicit SingleThreadProxy(LayerTreeHost* layer_tree_host);
 
-  bool CommitAndComposite(base::TimeTicks frame_begin_time);
+  bool CommitAndComposite(base::TimeTicks frame_begin_time,
+                          gfx::Rect device_viewport_damage_rect,
+                          LayerTreeHostImpl::FrameData* frame);
   void DoCommit(scoped_ptr<ResourceUpdateQueue> queue);
   bool DoComposite(
       scoped_refptr<cc::ContextProvider> offscreen_context_provider,
-      base::TimeTicks frame_begin_time);
+      base::TimeTicks frame_begin_time,
+      gfx::Rect device_viewport_damage_rect,
+      LayerTreeHostImpl::FrameData* frame);
   void DidSwapFrame();
 
   bool ShouldComposite() const;
 
   // Accessed on main thread only.
   LayerTreeHost* layer_tree_host_;
   bool output_surface_lost_;
   bool created_offscreen_context_provider_;
 
   // Holds on to the context between initializeContext() and
@@ skipping 70 matching lines @@
  private:
   DebugScopedSetImplThread impl_thread_;
   DebugScopedSetMainThreadBlocked main_thread_blocked_;
 
   DISALLOW_COPY_AND_ASSIGN(DebugScopedSetImplThreadAndMainThreadBlocked);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_SINGLE_THREAD_PROXY_H_