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
am: c65002b096

* commit 'c65002b096c4015e798a0ea685df0119c137b596':
  DO NOT MERGE MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: I228aaba5a714cdfa180bb368cc192c5c6260d33e