Add methods for telling V8 how much memory audio/video is using.

media/base/demuxer.h

Index: media/base/demuxer.h
diff --git a/media/base/demuxer.h b/media/base/demuxer.h
index 91f389d0175810f21c70b0985ada386855adec20..1f136a0cbcccd6e93f1ad85804407c9ecb1a4d04 100644
--- a/media/base/demuxer.h
+++ b/media/base/demuxer.h
@@ -87,6 +87,9 @@ class MEDIA_EXPORT Demuxer : public DemuxerStreamProvider {
   // a null Time is returned.
   virtual base::Time GetTimelineOffset() const = 0;
 
+  // Returns the memory usage in bytes for the demuxer.
+  virtual int64_t GetMemoryUsage() const = 0;
+
  private:
   DISALLOW_COPY_AND_ASSIGN(Demuxer);
 };