Calling maybeUpdateLegacyErrorState potentially creates a new legacy playback
state which involves calling player methods. This change makes sure that the call
sites of `maybeUpdateLegacyErrorState` are called on the app thread as enforced by
the library.
PiperOrigin-RevId: 476406282
(cherry picked from commit 74124f48ea838fcdb436726ba8337e82abc7552e)