After a period transition the first buffer queued has the sum of previous period
durations added to its source presentation timestamp. These durations take into
account gapless edits, but the check on the timestamp was based on the submitted
frame count, not the frame count after trimming.
This change fixes an issue where audio/video would gradually drift apart due to
accumulated error in the audio track position, which could lead to freezing due
to the audio renderer stopping being ready and switching to the standalone media
clock.
Issue: #4559
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=213819908
a0ab96623a