dispatchEvent is a regular method and it id executed synchronously. If you
call it twice, then the same group of listeners will be called twice in the
same call stack. If you want to manage the order in which handlers are
called you can specify priority when adding them, however, if you must add
many handlers (many would be hundreds) I would rethink using priority as the
handlers are sorted when added and the more handlers there are with the
certain priority specified, the slower the adding will be.
