Introduce AudioIPCFactory.

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 875bb9d122c57b11c778ee54051e32798544e72e..9fffd3677d9da0bcba1fd344c979606fa0b4f771 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -725,8 +725,12 @@ 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());
+  auto audio_message_filter =
+      base::MakeRefCounted<AudioMessageFilter>(GetIOTaskRunner());
+  AddFilter(audio_message_filter.get());
+  // TODO(maxmorin): Based on a feature flag, don't create the
+  // AudioMessageFilter, making AudioIPCFactory instead use mojo factories.
+  audio_ipc_factory_.emplace(audio_message_filter, GetIOTaskRunner());
 
   midi_message_filter_ = new MidiMessageFilter(GetIOTaskRunner());
   AddFilter(midi_message_filter_.get());