resolve merge conflicts of 823bd74 to lmp-mr1-dev am: 67ca3caf10 am: 6b52fd6b67 am: f4285f22bf am: 87406db29c am: 5f44938fe9
am: ff8818df6f

* commit 'ff8818df6f6bd07f80b9426af23a5f377e5843d6':
  MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: Ib96a7f164ba4846f33737f3388ea0c242af38636