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 0ef51fcadcba059560327ad5bf041224c5513ee2..b9550ddd5b9ade68b01cd2cc1f8b2c1b3a1df858 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -108,7 +108,6 @@
 #include "content/renderer/input/input_handler_manager.h"
 #include "content/renderer/input/main_thread_input_event_filter.h"
 #include "content/renderer/media/audio_input_message_filter.h"
-#include "content/renderer/media/audio_message_filter.h"
 #include "content/renderer/media/audio_renderer_mixer_manager.h"
 #include "content/renderer/media/media_stream_center.h"
 #include "content/renderer/media/midi_message_filter.h"
@@ -704,8 +703,7 @@ void RenderThreadImpl::Init(
   audio_input_message_filter_ = new AudioInputMessageFilter(GetIOTaskRunner());
   AddFilter(audio_input_message_filter_.get());
 
-  audio_message_filter_ = new AudioMessageFilter(GetIOTaskRunner());
-  AddFilter(audio_message_filter_.get());
+  audio_ipc_factory_.emplace(GetIOTaskRunner());
 
   midi_message_filter_ = new MidiMessageFilter(GetIOTaskRunner());
   AddFilter(midi_message_filter_.get());