report
Carries to the caller a change the widget published on one channel and reports on another: onChanged runs and the settling pass follows it, as in MirrorState.report, but the value itself was mirrored through MirrorState.observed when the earlier channel carried it.
A toggle is the shape that needs this. It publishes its selection to its item listener before it publishes the user's activation to its action listener, so a mirror riding the item channel has already recorded the change by the time the caller hears about it, and MirrorState.report would be answering a change MirrorState.observed has taken. Mirror on the earlier channel with MirrorState.observed, and report on the later one with this.
Runs on the event dispatch thread.
Parameters
run before the pass, so a caller that adopts the change is settled on what it wrote and one that does not is settled back onto its standing declaration.