Introduce AudioDecoderConfig to migrate away from GetAVStream().

media/filters/dummy_demuxer.cc

 // 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.
 
 #include "media/filters/dummy_demuxer.h"
 
 #include "base/logging.h"
 
 namespace media {
 
 DummyDemuxerStream::DummyDemuxerStream(Type type)
     : type_(type) {
 }
 
 DummyDemuxerStream::~DummyDemuxerStream() {}
 
 DemuxerStream::Type DummyDemuxerStream::type() {
   return type_;
 }
 
+AudioDecoderConfig* DummyDemuxerStream::audio_decoder_config() {
+  return NULL;
+}
+
 void DummyDemuxerStream::Read(const ReadCallback& read_callback) {}
 
 void DummyDemuxerStream::EnableBitstreamConverter() {}
 
 DummyDemuxer::DummyDemuxer(bool has_video, bool has_audio)
     : has_video_(has_video),
       has_audio_(has_audio) {
   streams_.resize(DemuxerStream::NUM_TYPES);
   if (has_audio)
     streams_[DemuxerStream::AUDIO] =
         new DummyDemuxerStream(DemuxerStream::AUDIO);
   if (has_video)
     streams_[DemuxerStream::VIDEO] =
         new DummyDemuxerStream(DemuxerStream::VIDEO);
 }
 
 DummyDemuxer::~DummyDemuxer() {}
 
 void DummyDemuxer::SetPreload(Preload preload) {}
 
 scoped_refptr<DemuxerStream> DummyDemuxer::GetStream(DemuxerStream::Type type) {
   return streams_[type];
 }
 
 base::TimeDelta DummyDemuxer::GetStartTime() const {
   return base::TimeDelta();
 }
 
 }  // namespace media