*/
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
final class ListenerCallQueue<L> {
  // TODO(cpovirk): consider using the logger associated with listener.getClass().
  private static final LazyLogger logger = new LazyLogger(ListenerCallQueue.class);

  // TODO(chrisn): promote AppendOnlyCollection for use here.
  private final List<PerListenerQueue<L>> listeners =