Let default device in PulseAudio be the system default device

media/audio/pulse/pulse_util.h

Index: media/audio/pulse/pulse_util.h
diff --git a/media/audio/pulse/pulse_util.h b/media/audio/pulse/pulse_util.h
index b8e5cdcda4c606eaef98770e1507bbff99522855..b71f5e3e5015a2464cdd928c75cac009accaf859 100644
--- a/media/audio/pulse/pulse_util.h
+++ b/media/audio/pulse/pulse_util.h
@@ -49,6 +49,16 @@ int GetHardwareLatencyInBytes(pa_stream* stream,
                               int sample_rate,
                               int bytes_per_frame);
 
+// pa_context_get_server_info callback. It's used by GetSystemDefaultInputDevice
+// to get the system default input device name.
+void SystemDefaultInputDeviceCallback(pa_context* context,
+                                      const pa_server_info* info,
+                                      void* user_data);
+
+// Return the system default input device name using pa_context_get_server_info.
+std::string GetSystemDefaultInputDevice(pa_threaded_mainloop* mainloop,
+                                        pa_context* context);
+
 // 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
@@ -61,6 +71,17 @@ bool CreateInputStream(pa_threaded_mainloop* mainloop,
                        pa_stream_notify_cb_t stream_callback,
                        void* user_data);
 
+// pa_context_get_server_info callback. It's used by
+// GetSystemDefaultOutputDevice to get the system default output device name.
+void SystemDefaultOutputDeviceCallback(pa_context* context,
+                                       const pa_server_info* info,
+                                       void* user_data);
+
+// Return the system default output device name using
+// pa_context_get_server_info.
+std::string GetSystemDefaultOutputDevice(pa_threaded_mainloop* mainloop,
+                                         pa_context* context);
+
 // 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