Let IPC::SyncMessageFilter take advantage of thread-safe Send.

ipc/ipc_channel_proxy.cc

 // 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.
 
 #include "ipc/ipc_channel_proxy.h"
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
@@ skipping 323 matching lines @@
   if (channel_send_thread_safe_) {
     SendFromThisThread(message);
     return;
   }
 
   ipc_task_runner()->PostTask(
       FROM_HERE, base::Bind(&ChannelProxy::Context::OnSendMessage, this,
                             base::Passed(scoped_ptr<Message>(message))));
 }
 
+bool ChannelProxy::Context::IsChannelSendThreadSafe() const {
+  return channel_send_thread_safe_;
+}
+
 //-----------------------------------------------------------------------------
 
 // static
 scoped_ptr<ChannelProxy> ChannelProxy::Create(
     const IPC::ChannelHandle& channel_handle,
     Channel::Mode mode,
     Listener* listener,
     const scoped_refptr<base::SingleThreadTaskRunner>& ipc_task_runner,
     AttachmentBroker* broker) {
   scoped_ptr<ChannelProxy> channel(new ChannelProxy(listener, ipc_task_runner));
@@ skipping 152 matching lines @@
 }
 #endif
 
 void ChannelProxy::SetAttachmentBrokerEndpoint(bool is_endpoint) {
   context()->set_attachment_broker_endpoint(is_endpoint);
 }
 
 //-----------------------------------------------------------------------------
 
 }  // namespace IPC