resolve merge conflicts of 823bd74 to lmp-mr1-dev am: 67ca3caf10
am: 6b52fd6b67

* commit '6b52fd6b673c44afc6fe57e85ef8b6994ea84659':
  MPEG4Extractor: ensure kKeyTrackID exists before creating an MPEG4Source as track.

Change-Id: I0e66a037649b0000c90c91b40af6eb587362c00b