Revert of Remove the last piece of deprecated synchronous IO code.

media/audio/audio_output_device.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.
 //
 // Audio rendering unit utilizing audio output stream provided by browser
 // process through IPC.
 //
 // Relationship of classes.
 //
 //  AudioOutputController                AudioOutputDevice
@@ skipping 63 matching lines @@
 class MEDIA_EXPORT AudioOutputDevice
     : NON_EXPORTED_BASE(public AudioRendererSink),
       NON_EXPORTED_BASE(public AudioOutputIPCDelegate),
       NON_EXPORTED_BASE(public ScopedTaskRunnerObserver) {
  public:
   // NOTE: Clients must call Initialize() before using.
   AudioOutputDevice(
       scoped_ptr<AudioOutputIPC> ipc,
       const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
 
-  // Initialize the stream using |session_id|, which is used for the browser
-  // to select the correct input device.
+  // Initialize function for clients wishing to have unified input and
+  // output, |params| may specify |input_channels| > 0, representing a
+  // number of input channels which will be at the same sample-rate
+  // and buffer-size as the output as specified in |params|. |session_id| is
+  // used for the browser to select the correct input device.
   void InitializeWithSessionId(const AudioParameters& params,
                                RenderCallback* callback,
                                int session_id);
 
   // AudioRendererSink implementation.
   virtual void Initialize(const AudioParameters& params,
                           RenderCallback* callback) OVERRIDE;
   virtual void Start() OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void Play() OVERRIDE;
@@ skipping 74 matching lines @@
   // TODO(scherkus): Replace this by changing AudioRendererSink to either accept
   // the callback via Start(). See http://crbug.com/151051 for details.
   bool stopping_hack_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputDevice);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_DEVICE_H_