cc: Make async readback path use async glRreadPixels.

cc/trees/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_THREAD_PROXY_H_
 #define CC_TREES_THREAD_PROXY_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time.h"
@@ skipping 144 matching lines @@
   void FinishAllRenderingOnImplThread(CompletionEvent* completion);
   void InitializeImplOnImplThread(CompletionEvent* completion,
                                   InputHandler* input_handler);
   void SetSurfaceReadyOnImplThread();
   void SetVisibleOnImplThread(CompletionEvent* completion, bool visible);
   void InitializeOutputSurfaceOnImplThread(
       scoped_ptr<OutputSurface> output_surface);
   void InitializeRendererOnImplThread(CompletionEvent* completion,
                                       bool* initialize_succeeded,
                                       RendererCapabilities* capabilities);
+  void FinishGLOnImplThread(CompletionEvent* completion);
   void LayerTreeHostClosedOnImplThread(CompletionEvent* completion);
   void ManageTilesOnImplThread();
   void AcquireLayerTexturesForMainThreadOnImplThread(
       CompletionEvent* completion);
   void RecreateOutputSurfaceOnImplThread(
       CompletionEvent* completion,
       scoped_ptr<OutputSurface> output_surface,
       scoped_refptr<cc::ContextProvider> offscreen_context_provider,
       bool* recreate_succeeded,
       RendererCapabilities* capabilities);
@@ skipping 83 matching lines @@
 
   base::TimeTicks smoothness_takes_priority_expiration_time_;
   bool renew_tree_priority_on_impl_thread_pending_;
 
   DISALLOW_COPY_AND_ASSIGN(ThreadProxy);
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_THREAD_PROXY_H_