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

* commit 'e83713c1987c929af2ed704e1a395a334606fad0':
  DO NOT MERGE MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: I683a737aa9379f46a5ffc3fdf33d1832942ffb38