This change masks playbackInfo.periodId and playbackInfo.loadingPeriodId for operations which change these periods (set/add/remove sources and seeks).
Because this masking is reflected in the playbackInfo object, player attributes can be retrieved without the maskingXyz variables in EPI. This has the advantage that the playbackInfo object always reflects the public state of the player even when operations are still pending. The maskingXyz variables in EPI are only required for the deprecated use case of an initial seek in an empty timeline.
PiperOrigin-RevId: 321160092
d62688cfc0