Refactor FFmpegVideoDecoder to try and generalize code common to all video decoders.

media/filters/ffmpeg_audio_decoder.h

 // Copyright (c) 2009 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_FILTERS_FFMPEG_AUDIO_DECODER_H_
 #define MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_
 
 #include "media/base/factory.h"
 #include "media/filters/decoder_base.h"
 
 struct AVCodecContext;
 
 namespace media {
 
 // Forward declaration for scoped_ptr_malloc.
 class ScopedPtrAVFree;
 
 class FFmpegAudioDecoder : public DecoderBase<AudioDecoder, Buffer> {
  public:
   static FilterFactory* CreateFactory() {
     return new FilterFactoryImpl0<FFmpegAudioDecoder>();
   }
 
   static bool IsMediaFormatSupported(const MediaFormat& media_format);
 
  protected:
-  virtual bool OnInitialize(DemuxerStream* demuxer_stream);
+  virtual void DoInitialize(DemuxerStream* demuxer_stream, bool* success,
+                            Task* done_cb);
 
-  virtual void OnSeek(base::TimeDelta time);
+  virtual void DoSeek(base::TimeDelta time, Task* done_cb);
 
-  virtual void OnStop();
-
-  virtual void OnDecode(Buffer* input);
+  virtual void DoDecode(Buffer* input, Task* done_cb);
 
  private:
   friend class FilterFactoryImpl0<FFmpegAudioDecoder>;
   FFmpegAudioDecoder();
   virtual ~FFmpegAudioDecoder();
 
   // Calculates the duration of an audio buffer based on the sample rate,
   // channels and bits per sample given the size in bytes.
   base::TimeDelta CalculateDuration(size_t size);
 
   // A FFmpeg defined structure that holds decoder information, this variable
   // is initialized in OnInitialize().
   AVCodecContext* codec_context_;
 
   // Estimated timestamp for next packet. Useful for packets without timestamps.
   base::TimeDelta estimated_next_timestamp_;
 
   // Data buffer to carry decoded raw PCM samples. This buffer is created by
   // av_malloc() and is used throughout the lifetime of this class.
   scoped_ptr_malloc<uint8, ScopedPtrAVFree> output_buffer_;
 
   static const size_t kOutputBufferSize;
 
   DISALLOW_COPY_AND_ASSIGN(FFmpegAudioDecoder);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_FFMPEG_AUDIO_DECODER_H_