When a live stream is joined while ads are already playing, the LOADED event is
missed and we don't have ad information for those ads in the ad group that are
before the ad index at which we joined. This way we can clip the duration when we
receive the LOADED event for the last ad in the group. This fixes the problem of
the playback controls being hidden when content resumes after the ad group.
#minor-release
PiperOrigin-RevId: 431269627
8e8c59031c