Handle audio device changes on Mac

media/audio/mac/audio_device_listener_mac.cc

Index: media/audio/mac/audio_device_listener_mac.cc
diff --git a/media/audio/mac/audio_device_listener_mac.cc b/media/audio/mac/audio_device_listener_mac.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3bae85df7f036447526bb183cf1d388c0599b1e3
--- /dev/null
+++ b/media/audio/mac/audio_device_listener_mac.cc
@@ -0,0 +1,98 @@
+// Copyright (c) 2012 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/mac/audio_device_listener_mac.h"
+
+#include <CoreAudio/CoreAudio.h>
+#include <vector>
+
+#include "base/logging.h"
+#include "base/mac/mac_logging.h"
+#include "base/synchronization/lock.h"
+
+namespace {
+
+class ListenerManager {
+ public:
+  ListenerManager();
+  void AddListener(media::AudioDeviceListenerMac* listener);
+  void RemoveListener(media::AudioDeviceListenerMac* listener);
+
+ private:
+  // Callback from system when the default device changes. This can be called
+  // either on the main thread or on a audio thread managed by the system
+  // (depending on what kAudioHardwarePropertyRunLoop is set to).
+  static OSStatus OnDefaultDeviceChanged(
+      AudioObjectID object,
+      UInt32 size,
+      const AudioObjectPropertyAddress addresses[],
+      void* context);
+
+  std::vector<media::AudioDeviceListenerMac*> listeners_;
+  base::Lock listener_lock_;
+};
+
+ListenerManager::ListenerManager() {
+  AudioObjectPropertyAddress property = {
+    kAudioHardwarePropertyDefaultOutputDevice,
+    kAudioObjectPropertyScopeGlobal,
+    kAudioObjectPropertyElementMaster
+  };
+  OSStatus result = AudioObjectAddPropertyListener(
+      kAudioObjectSystemObject,
+      &property,
+      &ListenerManager::OnDefaultDeviceChanged,
+      this);
+  OSSTATUS_DCHECK(result == noErr, result);
+}
+
+void ListenerManager::AddListener(media::AudioDeviceListenerMac* listener) {
+  base::AutoLock auto_lock(listener_lock_);
+  listeners_.push_back(listener);
+}
+
+void ListenerManager::RemoveListener(media::AudioDeviceListenerMac* listener) {
+  base::AutoLock auto_lock(listener_lock_);
+  listeners_.erase(std::find(listeners_.begin(), listeners_.end(), listener));
+}
+
+// static
+OSStatus ListenerManager::OnDefaultDeviceChanged(
+    AudioObjectID object,
+    UInt32 size,
+    const AudioObjectPropertyAddress addresses[],
+    void* context) {
+  ListenerManager* manager = static_cast<ListenerManager*>(context);
+  base::AutoLock auto_lock(manager->listener_lock_);
+  for (std::vector<media::AudioDeviceListenerMac*>::iterator it =
+       manager->listeners_.begin(); it != manager->listeners_.end(); ++it) {
+    (*it)->OnDefaultDeviceChanged();
+  }
+  return noErr;
+}
+
+ListenerManager* g_listener_manager = NULL;
+
+}  // namespace
+
+namespace media {
+
+AudioDeviceListenerMac::AudioDeviceListenerMac(const base::Closure& listener_cb)
+    : listener_cb_(listener_cb) {
+  if (!g_listener_manager)
+    g_listener_manager = new ListenerManager;
+  g_listener_manager->AddListener(this);
+}
+
+AudioDeviceListenerMac::~AudioDeviceListenerMac() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(g_listener_manager);
+  g_listener_manager->RemoveListener(this);
+}
+
+void AudioDeviceListenerMac::OnDefaultDeviceChanged() {
+  listener_cb_.Run();
+}
+
+}  // namespace media