chromecast: Cleanup class/struct fwd declarations

chromecast/media/cma/backend/alsa/audio_decoder_alsa.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_CMA_BACKEND_ALSA_AUDIO_DECODER_ALSA_H_
 #define CHROMECAST_MEDIA_CMA_BACKEND_ALSA_AUDIO_DECODER_ALSA_H_
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "chromecast/media/cma/backend/alsa/stream_mixer_alsa_input.h"
 #include "chromecast/media/cma/decoder/cast_audio_decoder.h"
 #include "chromecast/public/media/decoder_config.h"
 #include "chromecast/public/media/media_pipeline_backend.h"
 #include "chromecast/public/media/media_pipeline_device_params.h"
 
 namespace base {
 class SingleThreadTaskRunner;
-class Thread;
 }  // namespace base
 
 namespace chromecast {
 namespace media {
 class DecoderBufferBase;
 class MediaPipelineBackendAlsa;
 
 class AudioDecoderAlsa : public MediaPipelineBackend::AudioDecoder,
                          public StreamMixerAlsaInput::Delegate {
  public:
@@ skipping 56 matching lines @@
 
   base::WeakPtrFactory<AudioDecoderAlsa> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioDecoderAlsa);
 };
 
 }  // namespace media
 }  // namespace chromecast
 
 #endif  // CHROMECAST_MEDIA_CMA_BACKEND_ALSA_AUDIO_DECODER_ALSA_H_