Introduce AudioDecoderConfig to migrate away from GetAVStream().

media/base/demuxer_stream.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.
 
 #ifndef MEDIA_BASE_DEMUXER_STREAM_H_
 #define MEDIA_BASE_DEMUXER_STREAM_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "media/base/media_export.h"
 
 struct AVStream;
 
 namespace media {
 
+class AudioDecoderConfig;
 class Buffer;
 
 class MEDIA_EXPORT DemuxerStream
     : public base::RefCountedThreadSafe<DemuxerStream> {
  public:
   typedef base::Callback<void(Buffer*)> ReadCallback;
 
   enum Type {
     UNKNOWN,
     AUDIO,
     VIDEO,
     NUM_TYPES,  // Always keep this entry as the last one!
   };
 
   // Schedules a read.  When the |read_callback| is called, the downstream
   // object takes ownership of the buffer by AddRef()'ing the buffer.
   virtual void Read(const ReadCallback& read_callback) = 0;
 
   // Returns an |AVStream*| if supported, or NULL.
   virtual AVStream* GetAVStream();
 
+  // Returns the audio decoder configuration. It is an error to call this method
+  // if type() != AUDIO.
+  virtual const AudioDecoderConfig& audio_decoder_config() = 0;
+
   // Returns the type of stream.
   virtual Type type() = 0;
 
   virtual void EnableBitstreamConverter() = 0;
 
  protected:
   friend class base::RefCountedThreadSafe<DemuxerStream>;
   virtual ~DemuxerStream();
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_DEMUXER_STREAM_H_