It's not a comprehensive solution for setting the
playback speed because (a) it doesn't apply when
audio is disabled, and (b) we do some timestamp
interpolation in a few places where we assume real
time. However in practice it works pretty well and
most apps probably don't allow disabling of audio,
so I think it makes sense to expose it.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=123406605
