[GPU] Get GPU process running on the mac...

chrome/common/command_buffer_messages_internal.h

 // Copyright (c) 2009 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.
 
 #include "base/shared_memory.h"
 #include "ipc/ipc_message_macros.h"
 
 IPC_BEGIN_MESSAGES(CommandBuffer)
   // Initialize a command buffer with the given number of command entries.
   // Returns the shared memory handle for the command buffer mapped to the
@@ skipping 23 matching lines @@
   IPC_SYNC_MESSAGE_ROUTED1_0(CommandBufferMsg_DestroyTransferBuffer,
                              int32 /* id */)
 
   // Get the shared memory handle for a transfer buffer mapped to the callers
   // process.
   IPC_SYNC_MESSAGE_ROUTED1_2(CommandBufferMsg_GetTransferBuffer,
                              int32 /* id */,
                              base::SharedMemoryHandle /* transfer_buffer */,
                              size_t /* size */)
 
+#if defined(OS_MACOSX)
+  // On Mac OS X the GPU plugin must be offscreen, because there is no
+  // true cross-process window hierarchy. For this reason we must send
+  // resize events explicitly to the command buffer stub so it can
+  // reallocate its backing store and send the new one back to the
+  // browser. This message is currently used only on 10.6 and later.
+  IPC_MESSAGE_ROUTED2(CommandBufferMsg_SetWindowSize,
+                      int32 /* width */,
+                      int32 /* height */)
+#endif
+
 IPC_END_MESSAGES(CommandBuffer)