Revert of [chromecast] Pass media task runner to MediaPipelineBackendManager.

chromecast/media/audio/cast_audio_manager.h

 // Copyright 2015 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.
 
 #ifndef CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MANAGER_H_
 #define CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MANAGER_H_
 
 #include "base/macros.h"
 #include "media/audio/audio_manager_base.h"
 
 namespace chromecast {
 
 class TaskRunnerImpl;
 
 namespace media {
 
 class MediaPipelineBackend;
-class MediaPipelineBackendManager;
 struct MediaPipelineDeviceParams;
 
 class CastAudioManager : public ::media::AudioManagerBase {
  public:
-  // This class does not take ownership of |backend_manager|
-  CastAudioManager(::media::AudioLogFactory* audio_log_factory,
-                   MediaPipelineBackendManager* backend_manager);
+  explicit CastAudioManager(::media::AudioLogFactory* audio_log_factory);
   ~CastAudioManager() override;
 
   // AudioManager implementation.
   bool HasAudioOutputDevices() override;
   bool HasAudioInputDevices() override;
   void ShowAudioInputSettings() override;
   void GetAudioInputDeviceNames(
       ::media::AudioDeviceNames* device_names) override;
   ::media::AudioParameters GetInputStreamParameters(
       const std::string& device_id) override;
@@ skipping 13 matching lines @@
   ::media::AudioInputStream* MakeLinearInputStream(
       const ::media::AudioParameters& params,
       const std::string& device_id) override;
   ::media::AudioInputStream* MakeLowLatencyInputStream(
       const ::media::AudioParameters& params,
       const std::string& device_id) override;
   ::media::AudioParameters GetPreferredOutputStreamParameters(
       const std::string& output_device_id,
       const ::media::AudioParameters& input_params) override;
 
-  MediaPipelineBackendManager* const backend_manager_;
-
   DISALLOW_COPY_AND_ASSIGN(CastAudioManager);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MANAGER_H_