resolve merge conflicts of 823bd74 to lmp-mr1-dev am: 67ca3caf10 am: 6b52fd6b67 am: f4285f22bf am: 87406db29c am: 5f44938fe9 am: ff8818df6f
am: 266eacc66e  -s ours

* commit '266eacc66e8977c6baf0935bf35b8e74cf89b510':
  MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: Ib26a530ce9c3908030c6d70677a2f2c70193c371