Add mojo interface+impl for audio stream control.

media/audio/audio_output_delegate.cc

Index: media/audio/audio_output_delegate.cc
diff --git a/media/audio/audio_output_delegate.cc b/media/audio/audio_output_delegate.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6ac2b2e4262a4484cae97fc4cbe2f3c05b7fd303
--- /dev/null
+++ b/media/audio/audio_output_delegate.cc
@@ -0,0 +1,11 @@
+// Copyright 2017 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 "audio_output_delegate.h"
+
+media::AudioOutputDelegate::EventHandler::EventHandler() {}
+media::AudioOutputDelegate::EventHandler::~EventHandler() {}
+
+media::AudioOutputDelegate::AudioOutputDelegate() {}
+media::AudioOutputDelegate::~AudioOutputDelegate() {}