DO NOT MERGE MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track. am: b016207fc2 am: e2ca751723 am: 3d1df4f411  -s ours am: 1ed4ec584b  -s ours am: 4223af4708 am: e67ec85275 am: e83713c198  -s ours
am: 63a4f82181

* commit '63a4f82181744b6a6ca82226489a9138ef7823fb':
  DO NOT MERGE MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: Ic0bc3de3df2e071ec21789d8b11e50afc562c482