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
am: 886e91185e

* commit '886e91185e5288bd37c503a347d022ebbd1d32c2':
  MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: I33996a8f43905fd012232a56a783509bdbef568a