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 am: 28561389e9
am: 02d1d04498  -s ours

* commit '02d1d044981b6a28d18a72d7a897f50f446c3a80':
  DO NOT MERGE MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: I89f1f38e5db15e35a5d14cce11e9dd94a52c2677