Having one reorder event that superseeds another does not mean that the
dependant mutation events for the first reorder are obsolete. So we if we
coalesce a reorder event away we should leave its subordinate mutation events
alone.
The set of events fired to platform accessibility is not the same as the set in
the event queue. Therefore we should forward events to the parent process
someplace where they are the same so the same events can be emitted for child
processes.
