Cap the memory usage in FFMpegDemuxer.

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 ea2b9085f5d9a9e73b31887f459c3cd2df7c917b..32cba81bd7888cc7294d53e1ad936f7d606faf5b 100644
--- a/media/filters/ffmpeg_demuxer.h
+++ b/media/filters/ffmpeg_demuxer.h
@@ -94,6 +94,9 @@ class FFmpegDemuxerStream : public DemuxerStream {
   // Returns true if this stream has capacity for additional data.
   bool HasAvailableCapacity();
 
+  // Returns the total buffer size FFMpegDemuxerStream is holding onto.
+  size_t MemoryUsage() const;
+
   TextKind GetTextKind() const;
 
   // Returns the value associated with |key| in the metadata for the avstream.
@@ -182,6 +185,9 @@ class MEDIA_EXPORT FFmpegDemuxer : public Demuxer {
   // go over capacity depending on how the file is muxed.
   bool StreamsHaveAvailableCapacity();
 
+  // Returns true if the maximum allowed memory usage has been reached.
+  bool IsMaxMemoryUsageReached() const;
+
   // Signal all FFmpegDemuxerStreams that the stream has ended.
   void StreamHasEnded();