Support browser side thumbnailing for GPU composited pages on Windows.

ui/gfx/surface/accelerated_surface_win.h

 // Copyright (c) 2012 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_GFX_SURFACE_ACCELERATED_SURFACE_WIN_H_
 #define UI_GFX_SURFACE_ACCELERATED_SURFACE_WIN_H_
 #pragma once
 
 #include <d3d9.h>
 
@@ skipping 14 matching lines @@
 
   AcceleratedPresenter();
 
   // The public member functions are called on the main thread.
   void AsyncPresentAndAcknowledge(
       gfx::NativeWindow window,
       const gfx::Size& size,
       int64 surface_id,
       const base::Callback<void(bool)>& completion_task);
   bool Present(gfx::NativeWindow window);
+  bool CopyTo(const gfx::Size& size, void* buf);
   void Suspend();
   void WaitForPendingTasks();
 
  private:
   friend class base::RefCountedThreadSafe<AcceleratedPresenter>;
 
   ~AcceleratedPresenter();
 
   // These member functions are called on the PresentThread with which the
   // presenter has affinity.
@@ skipping 33 matching lines @@
   // this surface will be held while the completion callback runs.
   void AsyncPresentAndAcknowledge(
       gfx::NativeWindow window,
       const gfx::Size& size,
       int64 surface_id,
       const base::Callback<void(bool)>& completion_task);
 
   // Synchronously present a frame with no acknowledgement.
   bool Present(gfx::NativeWindow window);
 
+  // Copies the surface data to |buf|. The image data is transformed so that it
+  // fits in |size|.
+  // Caller must ensure that |buf| is allocated with the size no less than
+  // |4 * size.width() * size.height()| bytes.
+  bool CopyTo(const gfx::Size& size, void* buf);
+
   // Temporarily release resources until a new surface is asynchronously
   // presented. Present will not be able to represent the last surface after
   // calling this and will return false.
   void Suspend();
 
  private:
   scoped_refptr<AcceleratedPresenter> presenter_;
   DISALLOW_COPY_AND_ASSIGN(AcceleratedSurface);
 };
 
 #endif  // UI_GFX_SURFACE_ACCELERATED_SURFACE_WIN_H_