Add support for cancellation of demuxer reads.

media/filters/ffmpeg_demuxer.h

Index: media/filters/ffmpeg_demuxer.h
diff --git a/media/filters/ffmpeg_demuxer.h b/media/filters/ffmpeg_demuxer.h
index 1a95e11736c2b17eaaf3eb88a610b08ad1089e44..4e7822c2c6ad2dd978b7b2019d5ee8f2f7ffb66f 100644
--- a/media/filters/ffmpeg_demuxer.h
+++ b/media/filters/ffmpeg_demuxer.h
@@ -86,6 +86,9 @@ class FFmpegDemuxerStream : public DemuxerStream {
   // Empties the queues and ignores any additional calls to Read().
   void Stop();
 
+  // Aborts any pending reads.
+  void Abort();
+
   base::TimeDelta duration() const { return duration_; }
 
   // Enables fixes for files with negative timestamps.  Normally all timestamps
@@ -205,6 +208,7 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   void Initialize(DemuxerHost* host,
                   const PipelineStatusCB& status_cb,
                   bool enable_text_tracks) override;
+  void AbortPendingReads() override;
   void Stop() override;
   void StartWaitingForSeek(base::TimeDelta seek_time) override;
   void CancelPendingSeek(base::TimeDelta seek_time) override;