Revert of Pass task runners to AudioManager constructor.

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 572b99fe6b6fc4e155bf0c1a1bb9d47a7d319b01..97e3e3cfc78213b734333b3e18bc7f1b7fe4dcbc 100644
--- a/chromecast/media/audio/cast_audio_manager.h
+++ b/chromecast/media/audio/cast_audio_manager.h
@@ -20,11 +20,9 @@
 
 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(::media::AudioLogFactory* audio_log_factory,
+                   MediaPipelineBackendManager* backend_manager);
+  ~CastAudioManager() override;
 
   // AudioManager implementation.
   bool HasAudioOutputDevices() override;
@@ -39,9 +37,6 @@
   // See chromecast::media::MediaMessageLoop.
   virtual std::unique_ptr<MediaPipelineBackend> CreateMediaPipelineBackend(
       const MediaPipelineDeviceParams& params);
-
- protected:
-  ~CastAudioManager() override;
 
  private:
   // AudioManagerBase implementation.