Make ui::Snapshot asynchronous on Android, remove CompositeAndReadback.

ui/base/android/window_android_compositor.h

 // Copyright 2014 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 UI_BASE_ANDROID_WINDOW_ANDROID_COMPOSITOR_H_
 #define UI_BASE_ANDROID_WINDOW_ANDROID_COMPOSITOR_H_
 
+#include "cc/output/copy_output_request.h"
 #include "ui/base/ui_base_export.h"
 
 namespace cc {
 class Layer;
 }
 
 namespace ui {
 
 // Android interface for compositor-related tasks.
 class UI_BASE_EXPORT WindowAndroidCompositor {
  public:
   virtual ~WindowAndroidCompositor() {}
 
   virtual void AttachLayerForReadback(scoped_refptr<cc::Layer> layer) = 0;
+  virtual void RequestCopyOfOutputOnRootLayer(
+      scoped_ptr<cc::CopyOutputRequest> request) = 0;
   virtual void OnVSync(base::TimeTicks frame_time,
                        base::TimeDelta vsync_period) = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_ANDROID_WINDOW_ANDROID_COMPOSITOR_H_