Add a mojo implementation of AudioOutputIPC.

media/audio/audio_output_ipc.h

 // Copyright (c) 2012 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.
 
 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
 
 #include <string>
 
 #include "base/memory/shared_memory.h"
@@ skipping 79 matching lines @@
 
   // Starts playing the stream.  This should generate a call to
   // AudioOutputController::Play().
   virtual void PlayStream() = 0;
 
   // Pauses an audio stream.  This should generate a call to
   // AudioOutputController::Pause().
   virtual void PauseStream() = 0;
 
   // Closes the audio stream which should shut down the corresponding
-  // AudioOutputController in the peer process.
+  // AudioOutputController in the peer process. Usage of an AudioOutputIPC must
+  // always end with a call to CloseStream(), and the |delegate| passed to other
+  // method must remain valid until then. An exception is if OnIPCClosed is
+  // called first.
   virtual void CloseStream() = 0;
 
   // Sets the volume of the audio stream.
   virtual void SetVolume(double volume) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_