Add logic to poll AudioTimestamp at different rates depending on when
playback starts and how the audio timestamp advances.
This fixes a pause about 500 ms after starting playback that occurs on some
devices and also makes our polling interval match the recommendations of the
AudioTrack documentation.
Issue: #3830
Issue: #3841
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=189765200
