Merge "DO NOT MERGE - MPEG4Extractor: Check mLastTrack before dereferencing." into klp-dev am: 8caef85235 am: b512f4ab42 am: d18d8fac61  -s ours
am: 54c0001dc9  -s ours

Change-Id: I6bb100ce240464dff699c5d37227a93e085a2f74