Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/mac/audio_manager_mac.cc

Index: media/audio/mac/audio_manager_mac.cc
diff --git a/media/audio/mac/audio_manager_mac.cc b/media/audio/mac/audio_manager_mac.cc
index cb2ac1f1f2f7b8fce551096508bcafee56560f7c..86836e49bb2a5deb95af014a3a17485c18ae14de 100644
--- a/media/audio/mac/audio_manager_mac.cc
+++ b/media/audio/mac/audio_manager_mac.cc
@@ -418,13 +418,14 @@ AudioManagerMac::AudioManagerMac(
                             base::Unretained(this)));
 }
 
-AudioManagerMac::~AudioManagerMac() {
-  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
+AudioManagerMac::~AudioManagerMac() = default;
+
+void AudioManagerMac::Shutdown() {
   // We are now in shutdown mode. This flag disables MaybeChangeBufferSize()
   // and IncreaseIOBufferSizeIfPossible() which both touches native Core Audio
   // APIs and they can fail and disrupt tests during shutdown.
   in_shutdown_ = true;
-  Shutdown();
+  AudioManagerBase::Shutdown();
 }
 
 bool AudioManagerMac::HasAudioOutputDevices() {
@@ -1165,13 +1166,12 @@ void AudioManagerMac::ReleaseInputStream(AudioInputStream* stream) {
   AudioManagerBase::ReleaseInputStream(stream);
 }
 
-ScopedAudioManagerPtr CreateAudioManager(
+std::unique_ptr<AudioManager> CreateAudioManager(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
     AudioLogFactory* audio_log_factory) {
-  return ScopedAudioManagerPtr(
-      new AudioManagerMac(std::move(task_runner), std::move(worker_task_runner),
-                          audio_log_factory));
+  return base::MakeUnique<AudioManagerMac>(
+      std::move(task_runner), std::move(worker_task_runner), audio_log_factory);
 }
 
 }  // namespace media