Add GetAssociatedOutputDeviceID support to pulse.

media/audio/pulse/audio_manager_pulse.cc

Index: media/audio/pulse/audio_manager_pulse.cc
diff --git a/media/audio/pulse/audio_manager_pulse.cc b/media/audio/pulse/audio_manager_pulse.cc
index 398826ae1c360a03dcaebfcfea59e8be8e592adb..ccc5273b6a4c93fa0462f5f7deeca494c8e3b58d 100644
--- a/media/audio/pulse/audio_manager_pulse.cc
+++ b/media/audio/pulse/audio_manager_pulse.cc
@@ -174,6 +174,32 @@ AudioInputStream* AudioManagerPulse::MakeLowLatencyInputStream(
   return MakeInputStream(params, device_id);
 }
 
+std::string AudioManagerPulse::GetDefaultOutputDeviceID() {
+  return pulse::GetRealDefaultDeviceId(input_mainloop_, input_context_, false);
+}
+
+std::string AudioManagerPulse::GetAssociatedOutputDeviceID(
+    const std::string& input_device_id) {
+  DCHECK(AudioManager::Get()->GetTaskRunner()->BelongsToCurrentThread());
+  DCHECK(input_mainloop_);
+  DCHECK(input_context_);
+  std::string input;

[Guido Urdaneta, 2016/08/29 10:31:12]

use const ref to avoid copying in the case where input is not default 

[Max Morin, 2016/08/29 11:54:02]

Done.

+  if (input_device_id == AudioDeviceDescription::kDefaultDeviceId)
+    input =
+        pulse::GetRealDefaultDeviceId(input_mainloop_, input_context_, true);
+  else
+    input = input_device_id;
+
+  std::string input_bus =
+      pulse::GetBusOfInput(input_mainloop_, input_context_, input);
+  if (input_bus.empty()) {
+    return "";
+  }
+  std::string s = pulse::GetOutputCorrespondingTo(input_mainloop_,
+                                                  input_context_, input_bus);
+  return s;
+}
+
 AudioParameters AudioManagerPulse::GetPreferredOutputStreamParameters(
     const std::string& output_device_id,
     const AudioParameters& input_params) {