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

ipc/ipc_sync_channel.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_sync_channel.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/location.h"
 #include "base/logging.h"
@@ skipping 442 matching lines @@
   StartWatching();
 }
 
 SyncChannel::~SyncChannel() {
 }
 
 void SyncChannel::SetRestrictDispatchChannelGroup(int group) {
   sync_context()->set_restrict_dispatch_group(group);
 }
 
+scoped_refptr<IPC::SyncMessageFilter> SyncChannel::AddNewSyncMessageFilter() {

[jam, 2015/08/04 23:06:41]

nit: usually functions that return a new objects start with Create.. AddNewFoo
sounds like a method that takes a newly constructed object and adds it to a
container.

CreateSyncMessageFilter() would be clearer i think, and the comment can say that
it also adds it.

[Ken Rockot(use gerrit already), 2015/08/04 23:55:44]

Done.

+  scoped_refptr<IPC::SyncMessageFilter> filter = new IPC::SyncMessageFilter(

[jam, 2015/08/04 23:06:41]

nit: no IPC::

[Ken Rockot(use gerrit already), 2015/08/04 23:55:45]

Done.

+      sync_context()->shutdown_event(),
+      sync_context()->IsChannelSendThreadSafe());
+  AddFilter(filter.get());
+  return filter;
+}
+
 bool SyncChannel::Send(Message* message) {
 #ifdef IPC_MESSAGE_LOG_ENABLED
   std::string name;
   Logging::GetInstance()->GetMessageText(message->type(), &name, message, NULL);
   TRACE_EVENT1("ipc", "SyncChannel::Send", "name", name);
 #else
   TRACE_EVENT2("ipc", "SyncChannel::Send",
                "class", IPC_MESSAGE_ID_CLASS(message->type()),
                "line", IPC_MESSAGE_ID_LINE(message->type()));
 #endif
@@ skipping 105 matching lines @@
   // manual reset since the object watcher might otherwise reset the event
   // when we're doing a WaitMany.
   dispatch_watcher_callback_ =
       base::Bind(&SyncChannel::OnWaitableEventSignaled,
                   base::Unretained(this));
   dispatch_watcher_.StartWatching(sync_context()->GetDispatchEvent(),
                                   dispatch_watcher_callback_);
 }
 
 }  // namespace IPC