Use inner HWND for accelerated rendering on windows

chrome/gpu/gpu_command_buffer_stub.h

Index: chrome/gpu/gpu_command_buffer_stub.h
===================================================================
--- chrome/gpu/gpu_command_buffer_stub.h	(revision 66779)
+++ chrome/gpu/gpu_command_buffer_stub.h	(working copy)
@@ -51,6 +51,10 @@
 
   int32 route_id() const { return route_id_; }
 
+#if defined(OS_WIN)
+  void OnCompositorWindowPainted();
+#endif
+
  private:
   // Message handlers:
   void OnInitialize(int32 size, base::SharedMemoryHandle* ring_buffer);
@@ -70,6 +74,9 @@
 #if defined(OS_MACOSX)
   void OnSetWindowSize(const gfx::Size& size);
   void SwapBuffersCallback();
+#elif defined(OS_WIN)
+  void CreateCompositorWindow();
+  HWND compositor_window_;
 #endif
 
   // The lifetime of objects of this class is managed by a GpuChannel. The