Ensures that audio tasks cannot run after AudioManager is deleted.

chromecast/media/audio/cast_audio_manager.h

Index: chromecast/media/audio/cast_audio_manager.h
diff --git a/chromecast/media/audio/cast_audio_manager.h b/chromecast/media/audio/cast_audio_manager.h
index 677954eac15303e111e3e871a42ac61c3c78432c..f12264a046cea6fd1bbc4ecc0e00606c9c390c94 100644
--- a/chromecast/media/audio/cast_audio_manager.h
+++ b/chromecast/media/audio/cast_audio_manager.h
@@ -19,17 +19,14 @@ struct MediaPipelineDeviceParams;
 
 class CastAudioManager : public ::media::AudioManagerBase {
  public:
-  CastAudioManager(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-      scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
-      ::media::AudioLogFactory* audio_log_factory,
-      MediaPipelineBackendManager* backend_manager);
-  CastAudioManager(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-      scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
-      ::media::AudioLogFactory* audio_log_factory,
-      MediaPipelineBackendManager* backend_manager,
-      CastAudioMixer* audio_mixer);
+  CastAudioManager(std::unique_ptr<::media::AudioThread> audio_thread,
+                   ::media::AudioLogFactory* audio_log_factory,
+                   MediaPipelineBackendManager* backend_manager);
+  CastAudioManager(std::unique_ptr<::media::AudioThread> audio_thread,
+                   ::media::AudioLogFactory* audio_log_factory,
+                   MediaPipelineBackendManager* backend_manager,
+                   CastAudioMixer* audio_mixer);
+  ~CastAudioManager() override;
 
   // AudioManager implementation.
   bool HasAudioOutputDevices() override;
@@ -48,9 +45,6 @@ class CastAudioManager : public ::media::AudioManagerBase {
   virtual std::unique_ptr<MediaPipelineBackend> CreateMediaPipelineBackend(
       const MediaPipelineDeviceParams& params);
 
- protected:
-  ~CastAudioManager() override;
-
  private:
   // AudioManagerBase implementation.
   ::media::AudioOutputStream* MakeLinearOutputStream(