Add waitable event for SyncMessageFilter init

ipc/ipc_sync_message_filter.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 IPC_IPC_SYNC_MESSAGE_FILTER_H_
 #define IPC_IPC_SYNC_MESSAGE_FILTER_H_
 
 #include <set>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/scoped_vector.h"
 #include "base/synchronization/lock.h"
 #include "ipc/ipc_sender.h"
 #include "ipc/ipc_sync_message.h"
 #include "ipc/message_filter.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 class WaitableEvent;
 }
 
@@ skipping 30 matching lines @@
 
   // The process's main thread.
   scoped_refptr<base::SingleThreadTaskRunner> listener_task_runner_;
 
   // The message loop where the Channel lives.
   scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
 
   typedef std::set<PendingSyncMsg*> PendingSyncMessages;
   PendingSyncMessages pending_sync_messages_;
 
+  // Messages waiting to be delivered after IO initialization.
+  ScopedVector<Message> pending_messages_;
+
   // Locks data members above.
   base::Lock lock_;
 
   base::WaitableEvent* shutdown_event_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncMessageFilter);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_IPC_SYNC_MESSAGE_FILTER_H_