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 150 matching lines @@
   void SetVisibleOnImplThread(CompletionEvent* completion, bool visible);
   void HasInitializedOutputSurfaceOnImplThread(
       CompletionEvent* completion,
       bool* has_initialized_output_surface);
   void InitializeOutputSurfaceOnImplThread(
       CompletionEvent* completion,
       scoped_ptr<OutputSurface> output_surface,
       scoped_refptr<ContextProvider> offscreen_context_provider,
       bool* success,
       RendererCapabilities* capabilities);
+  void FinishGLOnImplThread(CompletionEvent* completion);
   void LayerTreeHostClosedOnImplThread(CompletionEvent* completion);
   void ManageTilesOnImplThread();
   void AcquireLayerTexturesForMainThreadOnImplThread(
       CompletionEvent* completion);
   ScheduledActionDrawAndSwapResult ScheduledActionDrawAndSwapInternal(
       bool forced_draw);
   void ForceSerializeOnSwapBuffersOnImplThread(CompletionEvent* completion);
   void SetNeedsForcedCommitOnImplThread();
   void CheckOutputSurfaceStatusOnImplThread();
   void CommitPendingOnImplThreadForTesting(CommitPendingRequest* request);
@@ skipping 73 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_