The stream offset is used to calculate the presentation time of
a metadata object when reading and later when playing, to calculate
the current presentation time to decide whether to send the metadata
to the output.
Accordingly, the presentation time of a pending metadata that has been
calculated with a given offset needs to be recalculated when the
stream offset changes.
#minor-release
PiperOrigin-RevId: 472499943
(cherry picked from commit 5a122377)
