Remove locking from FFmpegDemuxerStream and associated TODOs from media code.

media/filters/ffmpeg_video_decoder.h

Index: media/filters/ffmpeg_video_decoder.h
diff --git a/media/filters/ffmpeg_video_decoder.h b/media/filters/ffmpeg_video_decoder.h
index 47f542bb753a88409a6aac807de2fcef77ee3a2c..e95ceffdffe8eec03a15912cedfbba02c13ba6ca 100644
--- a/media/filters/ffmpeg_video_decoder.h
+++ b/media/filters/ffmpeg_video_decoder.h
@@ -56,10 +56,8 @@ class MEDIA_EXPORT FFmpegVideoDecoder : public VideoDecoder {
   // Carries out the reading operation scheduled by Read().
   void DoRead(const ReadCB& read_cb);
 
-  // Reads from the demuxer stream with corresponding callback method.
+  // Reads from the demuxer stream.
   void ReadFromDemuxerStream();
-  void DecryptOrDecodeBuffer(DemuxerStream::Status status,
-                             const scoped_refptr<DecoderBuffer>& buffer);
 
   // Carries out the buffer processing operation scheduled by
   // DecryptOrDecodeBuffer().