Use "application default" audio device as default PulseAudio device.

media/audio/pulse/pulse_util.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_PULSE_PULSE_UTIL_H_
 #define MEDIA_AUDIO_PULSE_PULSE_UTIL_H_
 
 #include <pulse/pulseaudio.h>
 
 #include "base/macros.h"
@@ skipping 35 matching lines @@
                                 pa_operation* operation);
 
 int GetHardwareLatencyInBytes(pa_stream* stream,
                               int sample_rate,
                               int bytes_per_frame);
 
 // Create a recording stream for the threaded mainloop, return true if success,
 // otherwise false. |mainloop| and |context| have to be from a valid Pulse
 // threaded mainloop and the handle of the created stream will be returned by
 // |stream|.
-// TODO(grunell): Move this function to PulseAudioInputStream class since it's
-// only used there.
 bool CreateInputStream(pa_threaded_mainloop* mainloop,
                        pa_context* context,
                        pa_stream** stream,
                        const AudioParameters& params,
                        const std::string& device_id,
                        pa_stream_notify_cb_t stream_callback,
                        void* user_data);
 
 // Create a playback stream for the threaded mainloop, return true if success,
 // otherwise false. This function will create a new Pulse threaded mainloop,
 // and the handles of the mainloop, context and stream will be returned by
 // |mainloop|, |context| and |stream|.
-// TODO(grunell): Move this function to PulseAudioOutputStream class since it's
-// only used there.
-bool CreateOutputStream(pa_threaded_mainloop* mainloop,
-                        pa_context* context,
+bool CreateOutputStream(pa_threaded_mainloop** mainloop,
+                        pa_context** context,
                         pa_stream** stream,
                         const AudioParameters& params,
                         const std::string& device_id,
                         const std::string& app_name,
                         pa_stream_notify_cb_t stream_callback,
                         pa_stream_request_cb_t write_callback,
                         void* user_data);
 
 }  // namespace pulse
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_PULSE_PULSE_UTIL_H_