To M56: Use ffmpeg for opus decoding, no need to maintain our decoder.

media/filters/opus_audio_decoder.h

-// Copyright (c) 2012 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_OPUS_AUDIO_DECODER_H_
-#define MEDIA_FILTERS_OPUS_AUDIO_DECODER_H_
-
-#include "base/callback.h"
-#include "base/macros.h"
-#include "base/time/time.h"
-#include "media/base/audio_decoder.h"
-#include "media/base/demuxer_stream.h"
-#include "media/base/sample_format.h"
-
-struct OpusMSDecoder;
-
-namespace base {
-class SingleThreadTaskRunner;
-}
-
-namespace media {
-
-class AudioBuffer;
-class AudioDiscardHelper;
-class DecoderBuffer;
-struct QueuedAudioBuffer;
-
-class MEDIA_EXPORT OpusAudioDecoder : public AudioDecoder {
- public:
-  explicit OpusAudioDecoder(
-      const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
-  ~OpusAudioDecoder() override;
-
-  // AudioDecoder implementation.
-  std::string GetDisplayName() const override;
-  void Initialize(const AudioDecoderConfig& config,
-                  CdmContext* cdm_context,
-                  const InitCB& init_cb,
-                  const OutputCB& output_cb) override;
-  void Decode(const scoped_refptr<DecoderBuffer>& buffer,
-              const DecodeCB& decode_cb) override;
-  void Reset(const base::Closure& closure) override;
-
- private:
-  // Reads from the demuxer stream with corresponding callback method.
-  void ReadFromDemuxerStream();
-  void DecodeBuffer(const scoped_refptr<DecoderBuffer>& input,
-                    const DecodeCB& decode_cb);
-
-  bool ConfigureDecoder();
-  void CloseDecoder();
-  void ResetTimestampState();
-  bool Decode(const scoped_refptr<DecoderBuffer>& input,
-              scoped_refptr<AudioBuffer>* output_buffer);
-
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-
-  AudioDecoderConfig config_;
-  OutputCB output_cb_;
-  OpusMSDecoder* opus_decoder_;
-  std::unique_ptr<AudioDiscardHelper> discard_helper_;
-
-  DISALLOW_IMPLICIT_CONSTRUCTORS(OpusAudioDecoder);
-};
-
-}  // namespace media
-
-#endif  // MEDIA_FILTERS_OPUS_AUDIO_DECODER_H_