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

content/child/child_thread_impl.cc

Index: content/child/child_thread_impl.cc
diff --git a/content/child/child_thread_impl.cc b/content/child/child_thread_impl.cc
index b0b7dd413de91ef89845930cc94a72104e0e24ff..367a12429cc61ed5435f33479804cf4b45ec73ea 100644
--- a/content/child/child_thread_impl.cc
+++ b/content/child/child_thread_impl.cc
@@ -366,8 +366,11 @@ void ChildThreadImpl::Init(const Options& options) {
 
   mojo_application_.reset(new MojoApplication(GetIOTaskRunner()));
 
-  sync_message_filter_ =
-      new IPC::SyncMessageFilter(ChildProcess::current()->GetShutDownEvent());
+  histogram_message_filter_ = new ChildHistogramMessageFilter();

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

why move this code?

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

only to preserve the order of the filters. reverted since this doesn't matter

+  channel_->AddFilter(histogram_message_filter_.get());
+
+  sync_message_filter_ = channel_->AddNewSyncMessageFilter();
+
   thread_safe_sender_ = new ThreadSafeSender(
       message_loop_->task_runner(), sync_message_filter_.get());
 
@@ -376,7 +379,6 @@ void ChildThreadImpl::Init(const Options& options) {
   websocket_dispatcher_.reset(new WebSocketDispatcher);
   file_system_dispatcher_.reset(new FileSystemDispatcher());
 
-  histogram_message_filter_ = new ChildHistogramMessageFilter();
   resource_message_filter_ =
       new ChildResourceMessageFilter(resource_dispatcher());
 
@@ -393,8 +395,6 @@ void ChildThreadImpl::Init(const Options& options) {
       new NotificationDispatcher(thread_safe_sender_.get());
   push_dispatcher_ = new PushDispatcher(thread_safe_sender_.get());
 
-  channel_->AddFilter(histogram_message_filter_.get());
-  channel_->AddFilter(sync_message_filter_.get());
   channel_->AddFilter(resource_message_filter_.get());
   channel_->AddFilter(quota_message_filter_->GetFilter());
   channel_->AddFilter(notification_dispatcher_->GetFilter());