Move media::AudioCodec to its own source file

media/filters/ffmpeg_audio_decoder.h

Index: media/filters/ffmpeg_audio_decoder.h
diff --git a/media/filters/ffmpeg_audio_decoder.h b/media/filters/ffmpeg_audio_decoder.h
index f56479abb37968e3df756ccc7b51e1c0c4dd7ce8..02fd02320ba533a9072b93fec7aea7d42158d35f 100644
--- a/media/filters/ffmpeg_audio_decoder.h
+++ b/media/filters/ffmpeg_audio_decoder.h
@@ -31,6 +31,8 @@ class DecoderBuffer;
 
 class MEDIA_EXPORT FFmpegAudioDecoder : public AudioDecoder {
  public:
+  static bool IsCodecSupported(AudioCodec codec, SampleFormat sample_format);

[jrummell, 2016/02/11 22:23:19]

I know that this matches what is in FFmpegVideoDecoder, but there are no callers
for it. Is this necessary? Do you have an upcoming need for it?

[DaleCurtis, 2016/02/11 22:26:42]

Yeah, I think callers should just invoke the ffmpeg method directly instead of
exposing this.

+
   FFmpegAudioDecoder(
       const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
       const scoped_refptr<MediaLog>& media_log);