cc: Setup API to release OutputSurface from LTHClient.

cc/trees/thread_proxy.h

Index: cc/trees/thread_proxy.h
diff --git a/cc/trees/thread_proxy.h b/cc/trees/thread_proxy.h
index 3aeef74b83f61e52d4f5c49c2f7aab0441fdb359..225b6016938d7b109642a9b05e3299cae14f9ebf 100644
--- a/cc/trees/thread_proxy.h
+++ b/cc/trees/thread_proxy.h
@@ -178,6 +178,7 @@ class CC_EXPORT ThreadProxy : public Proxy,
   bool MainFrameWillHappenForTesting() override;
   void SetChildrenNeedBeginFrames(bool children_need_begin_frames) override;
   void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval) override;
+  scoped_ptr<OutputSurface> ReleaseOutputSurface() override;
 
   // LayerTreeHostImplClient implementation
   void UpdateRendererCapabilitiesOnImplThread() override;
@@ -275,6 +276,7 @@ class CC_EXPORT ThreadProxy : public Proxy,
   void DeleteContentsTexturesOnImplThread(CompletionEvent* completion);
   void InitializeOutputSurfaceOnImplThread(
       scoped_ptr<OutputSurface> output_surface);
+  void ReleaseOutputSurfaceOnImplThread(CompletionEvent* completion);
   void FinishGLOnImplThread(CompletionEvent* completion);
   void LayerTreeHostClosedOnImplThread(CompletionEvent* completion);
   DrawResult DrawSwapInternal(bool forced_draw);
@@ -305,6 +307,8 @@ class CC_EXPORT ThreadProxy : public Proxy,
   CompositorThreadOnly compositor_thread_vars_unsafe_;
   CompositorThreadOnly& impl();
 
+  scoped_ptr<cc::OutputSurface> output_surface_;
+
   base::WeakPtr<ThreadProxy> main_thread_weak_ptr_;
   base::WeakPtr<ThreadProxy> impl_thread_weak_ptr_;