Add GetAssociatedOutputDeviceID support to pulse.

media/audio/pulse/audio_manager_pulse.cc

 // Copyright 2013 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.
 
 #include "media/audio/pulse/audio_manager_pulse.h"
 
 #include "base/command_line.h"
 #include "base/environment.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
@@ skipping 156 matching lines @@
 }
 
 AudioInputStream* AudioManagerPulse::MakeLowLatencyInputStream(
     const AudioParameters& params,
     const std::string& device_id,
     const LogCallback& log_callback) {
   DCHECK_EQ(AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
   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) {
   // TODO(tommi): Support |output_device_id|.
   VLOG_IF(0, !output_device_id.empty()) << "Not implemented!";
 
   ChannelLayout channel_layout = CHANNEL_LAYOUT_STEREO;
   int buffer_size = kMinimumOutputBufferSize;
   int bits_per_sample = 16;
   int sample_rate = GetNativeSampleRate();
@@ skipping 152 matching lines @@
 void AudioManagerPulse::SampleRateInfoCallback(pa_context* context,
                                                const pa_server_info* info,
                                                void* user_data) {
   AudioManagerPulse* manager = reinterpret_cast<AudioManagerPulse*>(user_data);
 
   manager->native_input_sample_rate_ = info->sample_spec.rate;
   pa_threaded_mainloop_signal(manager->input_mainloop_, 0);
 }
 
 }  // namespace media