Enable round-tripping and updating of WebSourceBufferImpl timestamp offset

media/filters/chunk_demuxer.h

Index: media/filters/chunk_demuxer.h
diff --git a/media/filters/chunk_demuxer.h b/media/filters/chunk_demuxer.h
index 857dcfd3e6c607c7aaf1bdbac356272d2e5f8e65..f74e2a832f4ec5e376a735a0041d2f153ac677ee 100644
--- a/media/filters/chunk_demuxer.h
+++ b/media/filters/chunk_demuxer.h
@@ -122,7 +122,11 @@ class MEDIA_EXPORT ChunkDemuxer : public Demuxer {
   // source buffer associated with |id|. Returns true if the offset is set
   // properly, false if the offset cannot be applied because we're in the
   // middle of parsing a media segment.
-  bool SetTimestampOffset(const std::string& id, base::TimeDelta offset);
+  bool SetTimestampOffset(const std::string& id, double offset);
+
+  // Retrieves the current offset being applied to subsequent buffers appended
+  // to the source buffer associated with |id|.
+  double GetTimestampOffset(const std::string& id);
 
   // Set the append mode to be applied to subsequent buffers appended to the
   // source buffer associated with |id|. If |sequence_mode| is true, caller