SDK / exoplayer

1. Ignore edit list where the sequence doesn't contain a sync
   sample, rather than failing.
2. Make Mp4Extractor.readAtomPayload so it doesn't try and read
   the same payload twice if a failure occurs parsing it.
3. Make processAtomEnded so that it doesn't pop the moov if
   parsing it fails.

Issue: #3351

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=172106244