media: Cleanup class/struct forward declarations

media/cdm/ppapi/external_clear_key/ffmpeg_cdm_audio_decoder.h

 // Copyright 2013 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 MEDIA_CDM_PPAPI_EXTERNAL_CLEAR_KEY_FFMPEG_CDM_AUDIO_DECODER_H_
 #define MEDIA_CDM_PPAPI_EXTERNAL_CLEAR_KEY_FFMPEG_CDM_AUDIO_DECODER_H_
 
 #include <stdint.h>
 
 #include <memory>
 #include <vector>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/time/time.h"
 #include "media/cdm/ppapi/external_clear_key/clear_key_cdm_common.h"
 #include "media/ffmpeg/ffmpeg_deleters.h"
 
 struct AVCodecContext;
 struct AVFrame;
 
 namespace media {
-class AudioBus;
 class AudioTimestampHelper;
 }
 
 namespace media {
 // TODO(xhwang): This class is partially cloned from FFmpegAudioDecoder. When
 // FFmpegAudioDecoder is updated, it's a pain to keep this class in sync with
 // FFmpegAudioDecoder. We need a long term sustainable solution for this. See
 // http://crbug.com/169203
 class FFmpegCdmAudioDecoder {
  public:
@@ skipping 53 matching lines @@
 
   typedef std::vector<uint8_t> SerializedAudioFrames;
   SerializedAudioFrames serialized_audio_frames_;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegCdmAudioDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_CDM_PPAPI_EXTERNAL_CLEAR_KEY_FFMPEG_CDM_AUDIO_DECODER_H_