Move parent of D3D surface window off the main GPU thread

gpu/ipc/service/child_window_surface_win.h

 // Copyright 2015 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 GPU_IPC_SERVICE_CHILD_WINDOW_SURFACE_WIN_H_
 #define GPU_IPC_SERVICE_CHILD_WINDOW_SURFACE_WIN_H_
 
 #include "ui/gl/gl_surface_egl.h"
 
 #include <windows.h>
@@ skipping 18 matching lines @@
 
  protected:
   ~ChildWindowSurfaceWin() override;
 
  private:
   void ClearInvalidContents();
 
   // This member contains all the data that can be accessed from the main or
   // window owner threads.
   std::unique_ptr<SharedData> shared_data_;
+  // The eventual parent of the window living in the browser process.
   HWND parent_window_;
+  // The window is initially created with this parent window. We need to keep it
+  // around so that we can destroy it at the end.
+  HWND initial_parent_window_;
   GpuChannelManager* manager_;
   bool alpha_;
   bool first_swap_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildWindowSurfaceWin);
 };
 
 }  // namespace gpu
 
 #endif  // GPU_IPC_SERVICE_CHILD_WINDOW_SURFACE_WIN_H_