MSE requires 'base-data-offset-present' not to be set, but FFmpeg may
generate fmp4 files with this flag though it actually uses moof as base.
Log a warning instead of failing directly in this case.
FFmpeg may also generates fmp4 files without tfdt box
(TrackFragmentDecodeTime) box, which is again non-MSE compliant. Handle
this scenario properly.
Bug: 18613712
Also fixes a test failure in SegmentTemplateTest introduced in an earlier
change.
Bug: 19235748
Change-Id: I4bcbb675b22a832a88cd33ee64c3e99a1c6e3a63