message: Make DomUtils.addCustomEventResender() more flexible about where it is exactly installed
diff: @@ -275,19 +275,23 @@ export function addCustomEventResender(listenTarget: EventTarget, eventName: str
  retransmitTarget: EventTarget=null): void {
  listenTarget.addEventListener(eventName, (ev: CustomEvent) => {
  - if (ev.target === listenTarget) {
  + const inflightResentEvent = inflightResentEvents.get(ev.target);
  + if (inflightResentEvent === ev && inflightResentEvent.type === eventName) {
  return;
  }
  ev.stopPropagation();
  -
  const detail = ev.detail;
  const bubbles = ev.bubbles;
  const event = new CustomEvent(eventName, { bubbles: bubbles, detail: detail });
  + inflightResentEvents.set(listenTarget, event);
  (retransmitTarget === null ? listenTarget : retransmitTarget).dispatchEvent(event);
  + inflightResentEvents.delete(listenTarget);
  });
  }
  +const inflightResentEvents = new Map<EventTarget, CustomEvent>();
  +
  //-------------------------------------------------------------------------
  export interface LaterHandle {
  