Masking is needed as soon as updates to a value can happen both in EPI
and EPII. PlayWhenReady is currently not masked because all updates
happen in EPI only. As soon as we allow pausing at certain times
(e.g. end of a stream), playWhenReady changes may be triggered by EPII
as well and that's why we need masking.
To know when the value actually changed, we also need to update the
internal state to include whether playback is supppressed.
PiperOrigin-RevId: 300284613
949bbcfb2e