Add IPC allowing GPU process to tell browser process to temporarily drop a front buffer.

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 "base/callback_forward.h"
 #include "base/memory/linked_ptr.h"
@@ skipping 12 matching lines @@
   // when it is safe to write to the surface on another thread. The lock for
   // this surface will be held while the completion callback runs.
   void AsyncPresentAndAcknowledge(HWND window,
                                   const gfx::Size& size,
                                   int64 surface_id,
                                   const base::Closure& completion_task);
 
   // Synchronously present a frame with no acknowledgement.
   bool Present(HWND window);
 
+  // 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:
   linked_ptr<AcceleratedPresenter> presenter_;
   DISALLOW_COPY_AND_ASSIGN(AcceleratedSurface);
 };
 
 #endif  // UI_GFX_SURFACE_ACCELERATED_SURFACE_WIN_H_