If compositor window already exists, then simply return it rather than compla...

chrome/common/gpu_messages_internal.h

 // Copyright (c) 2010 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.
 
 // This header is meant to be included in multiple passes, hence no traditional
 // header guard. It is included by backing_store_messages_internal.h
 // See ipc_message_macros.h for explanation of the macros and passes.
 
 // This file needs to be included again, even though we're actually included
 // from it via utility_messages.h.
@@ skipping 101 matching lines @@
   // order to uniquely identify the RenderWidgetHostView on the browser side.
   IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfaceSetIOSurface,
                        GpuHostMsg_AcceleratedSurfaceSetIOSurface_Params)
 
   // This message notifies the browser process that the renderer
   // swapped the buffers associated with the given "window", which
   // should cause the browser to redraw the compositor's contents.
   IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfaceBuffersSwapped,
                        GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params)
 #elif defined(OS_WIN)
-  // Create and get the HWND for the compositor window
-  IPC_SYNC_MESSAGE_CONTROL2_1(GpuHostMsg_CreateCompositorHostWindow,
+  // Get the HWND for the compositor window and if necessary, create it
+  IPC_SYNC_MESSAGE_CONTROL2_1(GpuHostMsg_GetCompositorHostWindow,
                               int32, /* renderer_id */
                               int32, /* render_view_id */
                               gfx::PluginWindowHandle /* compositor_host_id */)
 
   IPC_MESSAGE_CONTROL2(GpuHostMsg_ScheduleComposite,
                        int32, /* renderer_id */
                        int32 /* render_view_id */)
 #endif
 
 IPC_END_MESSAGES(GpuHost)
@@ skipping 208 matching lines @@
 
   // GpuVideoDecoder report output format change.
   IPC_MESSAGE_ROUTED1(GpuVideoDecoderHostMsg_MediaFormatChange,
                       GpuVideoDecoderFormatChangeParam)
 
   // GpuVideoDecoder report error.
   IPC_MESSAGE_ROUTED1(GpuVideoDecoderHostMsg_ErrorNotification,
                       GpuVideoDecoderErrorInfoParam)
 
 IPC_END_MESSAGES(GpuVideoDecoderHost)