Add a mojo implementation of AudioOutputIPC.

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index bd4ef1a6c6400f651419daaff4a67dff50dc3957..d3e16ca48c4978732607523f72637b4927f3c915 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -674,12 +674,17 @@ void RenderThreadImpl::Init(
 
 #endif  // BUILDFLAG(ENABLE_WEBRTC)
 
+  if (base::FeatureList::IsEnabled(
+          features::kUseMojoAudioOutputStreamFactory)) {
+    audio_ipc_factory_.emplace(GetIOTaskRunner());

[o1ka, 2017/04/20 10:36:00]

I'd prefer all the notion of kUseMojoAudioOutputStreamFactory to be hidden in
IPC factory.
audio_ipc_factory_ = AudioIPCFactory::Create(GetIOTaskRunner()); // no need for
optional
if (!audio_ipc_factory_) {
// create & reg a filter
}

[Max Morin, 2017/05/05 13:10:59]

I didn't do exactly this, PTAL.

+  } else {
+    audio_message_filter_ = new AudioMessageFilter(GetIOTaskRunner());
+    AddFilter(audio_message_filter_.get());
+  }
+
   audio_input_message_filter_ = new AudioInputMessageFilter(GetIOTaskRunner());
   AddFilter(audio_input_message_filter_.get());
 
-  audio_message_filter_ = new AudioMessageFilter(GetIOTaskRunner());
-  AddFilter(audio_message_filter_.get());
-
   midi_message_filter_ = new MidiMessageFilter(GetIOTaskRunner());
   AddFilter(midi_message_filter_.get());