chromecast: Cleanup class/struct fwd declarations

chromecast/media/audio/cast_audio_mixer.h

 // Copyright 2016 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_MIXER_H_
 #define CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MIXER_H_
 
 #include <memory>
 #include <vector>
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "media/audio/audio_io.h"
 #include "media/base/audio_converter.h"
 #include "media/base/audio_parameters.h"
 
 namespace chromecast {
 namespace media {
 
 class CastAudioManager;
-class CastAudioOutputStream;
 
 // CastAudioMixer mixes multiple AudioOutputStreams and passes the mixed
 // stream down to a single AudioOutputStream to be rendered by the CMA backend.
 class CastAudioMixer : public ::media::AudioOutputStream::AudioSourceCallback {
  public:
   using RealStreamFactory = base::Callback<::media::AudioOutputStream*(
       const ::media::AudioParameters&)>;
 
   explicit CastAudioMixer(const RealStreamFactory& real_stream_factory);
   ~CastAudioMixer() override;
@@ skipping 29 matching lines @@
 
   std::vector<MixerProxyStream*> proxy_streams_;
 
   DISALLOW_COPY_AND_ASSIGN(CastAudioMixer);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_AUDIO_CAST_AUDIO_MIXER_H_