Implement hook to change audio output device for PulseAudio.

media/audio/pulse/pulse_output.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.
 //
 // Creates an audio output stream based on the PulseAudio asynchronous API;
 // specifically using the pa_threaded_mainloop model.
 //
 // If the stream is successfully opened, Close() must be called before the
 // stream is deleted as Close() is responsible for ensuring resource cleanup
 // occurs.
 //
 // This object is designed so that all AudioOutputStream methods will be called
 // on the same thread that created the object.
 //
 // WARNING: This object blocks on internal PulseAudio calls in Open() while
 // waiting for PulseAudio's context structure to be ready.  It also blocks in
 // inside PulseAudio in Start() and repeated during playback, waiting for
 // PulseAudio write callbacks to occur.
 
 #ifndef MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_
 #define MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_
 
+#include <string>
+
 #include "base/memory/scoped_ptr.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_parameters.h"
 
 struct pa_context;
 struct pa_operation;
 struct pa_stream;
 struct pa_threaded_mainloop;
 
 namespace media {
 class AudioManagerBase;
 
 class PulseAudioOutputStream : public AudioOutputStream {
  public:
   PulseAudioOutputStream(const AudioParameters& params,
+                         const std::string& device_id,
                          AudioManagerBase* manager);
 
   virtual ~PulseAudioOutputStream();
 
   // Implementation of AudioOutputStream.
   virtual bool Open() OVERRIDE;
   virtual void Close() OVERRIDE;
   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
   virtual void Stop() OVERRIDE;
   virtual void SetVolume(double volume) OVERRIDE;
@@ skipping 11 matching lines @@
   // Fulfill a write request from the write request callback.  Outputs silence
   // if the request could not be fulfilled.
   void FulfillWriteRequest(size_t requested_bytes);
 
   // Close() helper function to free internal structs.
   void Reset();
 
   // AudioParameters from the constructor.
   const AudioParameters params_;
 
+  // The device ID for the device to open.
+  const std::string device_id_;
+
   // Audio manager that created us.  Used to report that we've closed.
   AudioManagerBase* manager_;
 
   // PulseAudio API structs.
   pa_context* pa_context_;
   pa_threaded_mainloop* pa_mainloop_;
   pa_stream* pa_stream_;
 
   // Float representation of volume from 0.0 to 1.0.
   float volume_;
 
   // Callback to audio data source.  Must only be modified while holding a lock
   // on |pa_mainloop_| via pa_threaded_mainloop_lock().
   AudioSourceCallback* source_callback_;
 
   // Container for retrieving data from AudioSourceCallback::OnMoreData().
   scoped_ptr<AudioBus> audio_bus_;
 
   DISALLOW_COPY_AND_ASSIGN(PulseAudioOutputStream);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_PULSE_PULSE_OUTPUT_H_