Cleanup AudioManager initialization on OSX to reduce startup delay.

Since the UI thread is the audio thread on OSX, we should be careful
about what we execute during startup.  Device enumeration and creation
of the device listener can be expensive, so don't do them until the
first stream is created.

BUG=288759
TEST=none

Review URL: https://codereview.chromium.org/154543002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251443 0039d316-1c4b-4281-b951-d872f2087c98

media/audio/mac/audio_manager_mac.cc

@@ -261,26 +261,25 @@ class AudioManagerMac::AudioPowerObserver : public base::PowerObserver {
 
 AudioManagerMac::AudioManagerMac(AudioLogFactory* audio_log_factory)
     : AudioManagerBase(audio_log_factory),
-      current_sample_rate_(0) {
-  current_output_device_ = kAudioDeviceUnknown;
-
+      current_sample_rate_(0),
+      current_output_device_(kAudioDeviceUnknown) {
   SetMaxOutputStreamsAllowed(kMaxOutputStreams);
 
   // Task must be posted last to avoid races from handing out "this" to the
   // audio thread.  Always PostTask even if we're on the right thread since
   // AudioManager creation is on the startup path and this may be slow.
   GetTaskRunner()->PostTask(FROM_HERE, base::Bind(
-      &AudioManagerMac::CreateDeviceListener, base::Unretained(this)));
+      &AudioManagerMac::InitializeOnAudioThread, base::Unretained(this)));
 }
 
 AudioManagerMac::~AudioManagerMac() {
   if (GetTaskRunner()->BelongsToCurrentThread()) {
-    DestroyDeviceListener();
+    ShutdownOnAudioThread();
   } else {
     // It's safe to post a task here since Shutdown() will wait for all tasks to
     // complete before returning.
     GetTaskRunner()->PostTask(FROM_HERE, base::Bind(
-        &AudioManagerMac::DestroyDeviceListener, base::Unretained(this)));
+        &AudioManagerMac::ShutdownOnAudioThread, base::Unretained(this)));
   }
 
   Shutdown();
@@ -565,6 +564,19 @@ AudioOutputStream* AudioManagerMac::MakeLowLatencyOutputStream(
     DLOG(ERROR) << "Failed to open output device: " << device_id;
     return NULL;
   }
+
+  // Lazily create the audio device listener on the first stream creation.
+  if (!output_device_listener_) {
+    output_device_listener_.reset(new AudioDeviceListenerMac(base::Bind(
+        &AudioManagerMac::HandleDeviceChanges, base::Unretained(this))));
+    // Only set the current output device for the default device.
+    if (device_id == AudioManagerBase::kDefaultDeviceId || device_id.empty())
+      current_output_device_ = device;
+    // Just use the current sample rate since we don't allow non-native sample
+    // rates on OSX.
+    current_sample_rate_ = params.sample_rate();
+  }
+
   return new AUHALStream(this, params, device);
 }
 
@@ -675,21 +687,12 @@ AudioParameters AudioManagerMac::GetPreferredOutputStreamParameters(
       AudioParameters::NO_EFFECTS);
 }
 
-void AudioManagerMac::CreateDeviceListener() {
+void AudioManagerMac::InitializeOnAudioThread() {
   DCHECK(GetTaskRunner()->BelongsToCurrentThread());
-
-  // Get a baseline for the sample-rate and current device,
-  // so we can intelligently handle device notifications only when necessary.
-  current_sample_rate_ = HardwareSampleRate();
-  if (!GetDefaultOutputDevice(&current_output_device_))
-    current_output_device_ = kAudioDeviceUnknown;
-
-  output_device_listener_.reset(new AudioDeviceListenerMac(base::Bind(
-      &AudioManagerMac::HandleDeviceChanges, base::Unretained(this))));
   power_observer_.reset(new AudioPowerObserver());
 }
 
-void AudioManagerMac::DestroyDeviceListener() {
+void AudioManagerMac::ShutdownOnAudioThread() {
   DCHECK(GetTaskRunner()->BelongsToCurrentThread());
   output_device_listener_.reset();
   power_observer_.reset();

media/audio/mac/audio_manager_mac.h

@@ -78,9 +78,8 @@ class MEDIA_EXPORT AudioManagerMac : public AudioManagerBase {
       const AudioParameters& input_params) OVERRIDE;
 
  private:
-  // Helper methods for constructing AudioDeviceListenerMac on the audio thread.
-  void CreateDeviceListener();
-  void DestroyDeviceListener();
+  void InitializeOnAudioThread();
+  void ShutdownOnAudioThread();
 
   int ChooseBufferSize(int output_sample_rate);