chromecast: Cleanup class/struct fwd declarations

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 CastAudioMixer;
 class MediaPipelineBackend;
 class MediaPipelineBackendManager;
 struct MediaPipelineDeviceParams;
 
 class CastAudioManager : public ::media::AudioManagerBase {
  public:
   CastAudioManager(
@@ skipping 56 matching lines @@
   std::unique_ptr<::media::AudioOutputStream> mixer_output_stream_;
   std::unique_ptr<CastAudioMixer> mixer_;
 
   DISALLOW_COPY_AND_ASSIGN(CastAudioManager);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MANAGER_H_