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

components/nacl/loader/nacl_listener.cc

 // Copyright 2013 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 "components/nacl/loader/nacl_listener.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <stdlib.h>
 #include <string.h>
@@ skipping 244 matching lines @@
  private:
   ~FileTokenMessageFilter() override {}
 };
 
 void NaClListener::Listen() {
   std::string channel_name =
       base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           switches::kProcessChannelID);
   channel_ = IPC::SyncChannel::Create(this, io_thread_.task_runner().get(),
                                       &shutdown_event_);
-  filter_ = new IPC::SyncMessageFilter(&shutdown_event_);
-  channel_->AddFilter(filter_.get());
+  filter_ = channel_->CreateSyncMessageFilter();
   channel_->AddFilter(new FileTokenMessageFilter());
   channel_->Init(channel_name, IPC::Channel::MODE_CLIENT, true);
   main_loop_ = base::MessageLoop::current();
   main_loop_->Run();
 }
 
 bool NaClListener::OnMessageReceived(const IPC::Message& msg) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(NaClListener, msg)
       IPC_MESSAGE_HANDLER(NaClProcessMsg_AddPrefetchedResource,
@@ skipping 219 matching lines @@
 }
 
 void NaClListener::OnFileTokenResolved(
     uint64_t token_lo,
     uint64_t token_hi,
     IPC::PlatformFileForTransit ipc_fd,
     base::FilePath file_path) {
   resolved_cb_.Run(ipc_fd, file_path);
   resolved_cb_.Reset();
 }