Wire up the output device id and provide an implementation on Windows.

media/audio/win/audio_low_latency_output_win.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.
 
 // Implementation of AudioOutputStream for Windows using Windows Core Audio
 // WASAPI for low latency rendering.
 //
 // Overview of operation and performance:
 //
 // - An object of WASAPIAudioOutputStream is created by the AudioManager
@@ skipping 104 matching lines @@
 class AudioManagerWin;
 
 // AudioOutputStream implementation using Windows Core Audio APIs.
 class MEDIA_EXPORT WASAPIAudioOutputStream :
       public AudioOutputStream,
       public base::DelegateSimpleThread::Delegate {
  public:
   // The ctor takes all the usual parameters, plus |manager| which is the
   // the audio manager who is creating this object.
   WASAPIAudioOutputStream(AudioManagerWin* manager,
+                          const std::string& device_id,
                           const AudioParameters& params,
                           ERole device_role);
 
   // The dtor is typically called by the AudioManager only and it is usually
   // triggered by calling AudioOutputStream::Close().
   virtual ~WASAPIAudioOutputStream();
 
   // Implementation of AudioOutputStream.
   virtual bool Open() OVERRIDE;
   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
@@ skipping 78 matching lines @@
 
   // Size in bytes of each audio packet.
   size_t packet_size_bytes_;
 
   // Size in milliseconds of each audio packet.
   float packet_size_ms_;
 
   // Length of the audio endpoint buffer.
   uint32 endpoint_buffer_size_frames_;
 
+  // The target device id or an empty string for the default device.
+  const std::string device_id_;
+
   // Defines the role that the system has assigned to an audio endpoint device.
   ERole device_role_;
 
   // The sharing mode for the connection.
   // Valid values are AUDCLNT_SHAREMODE_SHARED and AUDCLNT_SHAREMODE_EXCLUSIVE
   // where AUDCLNT_SHAREMODE_SHARED is the default.
   AUDCLNT_SHAREMODE share_mode_;
 
   // Counts the number of audio frames written to the endpoint buffer.
   UINT64 num_written_frames_;
@@ skipping 21 matching lines @@
 
   // Container for retrieving data from AudioSourceCallback::OnMoreData().
   scoped_ptr<AudioBus> audio_bus_;
 
   DISALLOW_COPY_AND_ASSIGN(WASAPIAudioOutputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_OUTPUT_WIN_H_