Let default device in PulseAudio be the system default device

media/audio/pulse/pulse_output.cc

Index: media/audio/pulse/pulse_output.cc
diff --git a/media/audio/pulse/pulse_output.cc b/media/audio/pulse/pulse_output.cc
index 953f9acebfacf10e06b754c2c28b93adb6bd23e8..c06093e1f4390ccfdacdd64614be25a6a0d8c839 100644
--- a/media/audio/pulse/pulse_output.cc
+++ b/media/audio/pulse/pulse_output.cc
@@ -61,10 +61,102 @@ PulseAudioOutputStream::~PulseAudioOutputStream() {
   DCHECK(!pa_mainloop_);
 }
 
+bool PulseAudioOutputStream::InitializeMainloopAndContext() {
+  DCHECK(!pa_mainloop_);
+  DCHECK(!pa_context_);
+  DCHECK(thread_checker_.CalledOnValidThread());
+  pa_mainloop_ = pa_threaded_mainloop_new();
+  if (!pa_mainloop_) {
+    DLOG(ERROR) << "Failed to create PulseAudio main loop.";
+    return false;
+  }
+
+  pa_mainloop_api* pa_mainloop_api = pa_threaded_mainloop_get_api(pa_mainloop_);
+  std::string app_name = AudioManager::GetGlobalAppName();
+  pa_context_ = pa_context_new(
+      pa_mainloop_api, app_name.empty() ? "Chromium" : app_name.c_str());
+  if (!pa_context_) {
+    DLOG(ERROR) << "Failed to create PulseAudio context.";
+    return false;
+  }
+
+  // A state callback must be set before calling pa_threaded_mainloop_lock() or
+  // pa_threaded_mainloop_wait() calls may lead to dead lock.
+  pa_context_set_state_callback(pa_context_, &pulse::ContextStateCallback,
+                                pa_mainloop_);
+  {
+    // Lock the main loop while setting up the context.  Failure to do so may
+    // lead to crashes as the PulseAudio thread tries to run before things are
+    // ready.
+    AutoPulseLock auto_lock(pa_mainloop_);
+
+    if (pa_threaded_mainloop_start(pa_mainloop_) != 0) {
+      DLOG(ERROR) << "Failed to start PulseAudio main loop.";
+      return false;
+    }
+
+    if (pa_context_connect(pa_context_, NULL, PA_CONTEXT_NOAUTOSPAWN, NULL) !=
+        0) {
+      DLOG(ERROR) << "Failed to connect PulseAudio context.";
+      return false;
+    }
+
+    // Wait until |pa_context_| is ready.  pa_threaded_mainloop_wait() must be
+    // called after pa_context_get_state() in case the context is already ready,
+    // otherwise pa_threaded_mainloop_wait() will hang indefinitely.
+    while (true) {
+      pa_context_state_t context_state = pa_context_get_state(pa_context_);
+      if (!PA_CONTEXT_IS_GOOD(context_state)) {
+        DLOG(ERROR) << "Invalid PulseAudio context state.";
+        return false;
+      }
+
+      if (context_state == PA_CONTEXT_READY)
+        break;
+      pa_threaded_mainloop_wait(pa_mainloop_);
+    }
+  }
+
+  return true;
+}
+
+// static, used by pa_context_get_server_info.
+void PulseAudioOutputStream::GetSystemDefaultOutputDeviceCallback(
+    pa_context* context,
+    const pa_server_info* info,
+    void* user_data) {
+  media::PulseAudioOutputStream* stream =
+      static_cast<media::PulseAudioOutputStream*>(user_data);
+  stream->default_system_device_name_ = info->default_sink_name;
+  pa_threaded_mainloop_signal(stream->pa_mainloop_, 0);
+}
+
+void PulseAudioOutputStream::GetSystemDefaultOutputDevice() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(pa_mainloop_);
+  DCHECK(pa_context_);
+  pa_operation* operation = pa_context_get_server_info(
+      pa_context_, PulseAudioOutputStream::GetSystemDefaultOutputDeviceCallback,
+      this);
+  WaitForOperationCompletion(pa_mainloop_, operation);
+}
+
 bool PulseAudioOutputStream::Open() {
   DCHECK(thread_checker_.CalledOnValidThread());
+  if (!InitializeMainloopAndContext()) {
+    return false;
+  }
+
+  AutoPulseLock auto_lock(pa_mainloop_);
+
+  std::string device_name_to_use = device_id_;
+  if (device_id_ == AudioManagerBase::kDefaultDeviceId) {
+    GetSystemDefaultOutputDevice();
+    device_name_to_use = default_system_device_name_;
+  }
+
   return pulse::CreateOutputStream(
-      &pa_mainloop_, &pa_context_, &pa_stream_, params_, device_id_,
+      pa_mainloop_, pa_context_, &pa_stream_, params_, device_name_to_use,
       AudioManager::GetGlobalAppName(), &StreamNotifyCallback,
       &StreamRequestCallback, this);
 }