The player already supports changing durations of periods and ads.
The only thing not yet supported is a change in ad break positions
which changes the duration of clipped content ending in an ad break.
Adding support for this requires updating the end position in
MediaPeriodInfo and changing the clip end position of the respective
ClippingMediaPeriod.
Issue: #5067
PiperOrigin-RevId: 373139724
08fb7bd65f