The positions in the SeekHead element should be relative to the
Segment payload, not the start of the file. Also added entries for
Tracks and SegmentInfo.
Change-Id: Id692da25fffc27d78e9f1a06d061431aeb6f1e7c
* Added WebM muxer that supports both single and multi-segment modes.
* WebM muxer supports MPD generation.
* Enabled WebM muxer and demuxer in packager.
b/22463220
b/25089245
b/25089714
Change-Id: I9f6e8fc51e08fbb1d685229c5cb54ea60f7bed8f