Introduce AudioDecoderConfig to migrate away from GetAVStream().

media/filters/dummy_demuxer.h

 // Copyright (c) 2011 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.
 
 // Implements the Demuxer interface. DummyDemuxer returns corresponding
 // DummyDemuxerStream as signal for media pipeline to construct correct
 // playback channels.
 
 #ifndef MEDIA_FILTERS_DUMMY_DEMUXER_H_
 #define MEDIA_FILTERS_DUMMY_DEMUXER_H_
 
 #include <vector>
 
+#include "media/base/audio_decoder_config.h"
 #include "media/base/demuxer.h"
 
 namespace media {
 
 class DummyDemuxerStream : public DemuxerStream {
  public:
   explicit DummyDemuxerStream(Type type);
 
   // DemuxerStream implementation.
   virtual void Read(const ReadCallback& read_callback) OVERRIDE;
   virtual Type type() OVERRIDE;
+  virtual const AudioDecoderConfig& audio_decoder_config() OVERRIDE;
   virtual void EnableBitstreamConverter() OVERRIDE;
 
  private:
   virtual ~DummyDemuxerStream();
 
   Type type_;
+  AudioDecoderConfig audio_config_;
 
   DISALLOW_COPY_AND_ASSIGN(DummyDemuxerStream);
 };
 
 class DummyDemuxer : public Demuxer {
  public:
   DummyDemuxer(bool has_video, bool has_audio);
   virtual ~DummyDemuxer();
 
   // Demuxer implementation.
   virtual scoped_refptr<DemuxerStream> GetStream(
       DemuxerStream::Type type) OVERRIDE;
   virtual void SetPreload(Preload preload) OVERRIDE;
   virtual base::TimeDelta GetStartTime() const OVERRIDE;
 
  private:
   bool has_video_;
   bool has_audio_;
   std::vector< scoped_refptr<DummyDemuxerStream> > streams_;
 
   DISALLOW_COPY_AND_ASSIGN(DummyDemuxer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_FILTERS_DUMMY_DEMUXER_H_