1 files changed, 69 insertions, 18 deletions

diff --git a/media/audio/mac/audio_manager_mac.cc b/media/audio/mac/audio_manager_mac.cc
index 288ac14..e0300ed 100644
--- a/media/audio/mac/audio_manager_mac.cc
+++ b/media/audio/mac/audio_manager_mac.cc
@@ -233,20 +233,74 @@ static AudioDeviceID GetAudioDeviceIdByUId(bool is_input,
   return audio_device_id;
 }
 
-AudioManagerMac::AudioManagerMac() {
+// Property address to monitor for device changes.
+static const AudioObjectPropertyAddress kDeviceChangePropertyAddress = {
+  kAudioHardwarePropertyDefaultOutputDevice,
+  kAudioObjectPropertyScopeGlobal,
+  kAudioObjectPropertyElementMaster
+};
+
+// Callback from the system when the default device changes; this must be called
+// on the MessageLoop that created the AudioManager.
+static OSStatus OnDefaultDeviceChangedCallback(
+    AudioObjectID object,
+    UInt32 num_addresses,
+    const AudioObjectPropertyAddress addresses[],
+    void* context) {
+  if (object != kAudioObjectSystemObject)
+    return noErr;
+
+  for (UInt32 i = 0; i < num_addresses; ++i) {
+    if (addresses[i].mSelector == kDeviceChangePropertyAddress.mSelector &&
+        addresses[i].mScope == kDeviceChangePropertyAddress.mScope &&
+        addresses[i].mElement == kDeviceChangePropertyAddress.mElement &&
+        context) {
+      static_cast<AudioManagerMac*>(context)->OnDeviceChange();
+      break;
+    }
+  }
+
+  return noErr;
+}
+
+AudioManagerMac::AudioManagerMac()
+    : listener_registered_(false),
+      creating_message_loop_(base::MessageLoopProxy::current()) {
   SetMaxOutputStreamsAllowed(kMaxOutputStreams);
 
-  // Task must be posted last to avoid races from handing out "this" to the
-  // audio thread.
-  GetMessageLoop()->PostTask(FROM_HERE, base::Bind(
-      &AudioManagerMac::CreateDeviceListener, base::Unretained(this)));
+  // AudioManagerMac is expected to be created by the root platform thread, this
+  // is generally BrowserMainLoop, it's MessageLoop will drive the NSApplication
+  // pump which in turn fires the property listener callbacks.
+  if (!creating_message_loop_)
+    return;
+
+  OSStatus result = AudioObjectAddPropertyListener(
+      kAudioObjectSystemObject,
+      &kDeviceChangePropertyAddress,
+      &OnDefaultDeviceChangedCallback,
+      this);
+
+  if (result != noErr) {
+    OSSTATUS_DLOG(ERROR, result) << "AudioObjectAddPropertyListener() failed!";
+    return;
+  }
+
+  listener_registered_ = true;
 }
 
 AudioManagerMac::~AudioManagerMac() {
-  // It's safe to post a task here since Shutdown() will wait for all tasks to
-  // complete before returning.
-  GetMessageLoop()->PostTask(FROM_HERE, base::Bind(
-      &AudioManagerMac::DestroyDeviceListener, base::Unretained(this)));
+  if (listener_registered_) {
+    // TODO(dalecurtis): CHECK destruction happens on |creating_message_loop_|,
+    // should be true, but currently several unit tests perform destruction in
+    // odd places so we can't CHECK here currently.
+    OSStatus result = AudioObjectRemovePropertyListener(
+        kAudioObjectSystemObject,
+        &kDeviceChangePropertyAddress,
+        &OnDefaultDeviceChangedCallback,
+        this);
+    OSSTATUS_DLOG_IF(ERROR, result != noErr, result)
+        << "AudioObjectRemovePropertyListener() failed!";
+  }
 
   Shutdown();
 }
@@ -335,17 +389,14 @@ AudioParameters AudioManagerMac::GetPreferredLowLatencyOutputStreamParameters(
       input_params);
 }
 
-void AudioManagerMac::CreateDeviceListener() {
-  DCHECK(GetMessageLoop()->BelongsToCurrentThread());
-  output_device_listener_.reset(new AudioDeviceListenerMac(BindToLoop(
+void AudioManagerMac::OnDeviceChange() {
+  // Post the task to the |creating_message_loop_| to execute our listener
+  // callback.  The callback is created using BindToLoop() so will hop over
+  // to the audio thread upon execution.
+  creating_message_loop_->PostTask(FROM_HERE, BindToLoop(
       GetMessageLoop(), base::Bind(
           &AudioManagerMac::NotifyAllOutputDeviceChangeListeners,
-          base::Unretained(this)))));
-}
-
-void AudioManagerMac::DestroyDeviceListener() {
-  DCHECK(GetMessageLoop()->BelongsToCurrentThread());
-  output_device_listener_.reset();
+          base::Unretained(this))));
 }
 
 AudioManager* CreateAudioManager() {