resolve merge conflicts of 823bd74 to lmp-mr1-dev
am: 67ca3caf10

* commit '67ca3caf10929022b2b742b49a88ff1238d3bbe7':
  MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: Ib76faa0fc2fd5a854f40b5c31fe7c8bfe0d6e3d6