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

* commit '28561389e9c344cbc699b58ad5b490505e9342b1':
  DO NOT MERGE MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: I0efe507b0689e3491dd8590b3f0b04629bc39f57