code: @EventThread
      protected void clientSessionWillEnd (final PresentsSession session)
      {
          // notify the observers that the session is ended
          _dclobservers.apply(new ObserverList.ObserverOp<DetailedClientObserver>() {
              public boolean apply (DetailedClientObserver observer) {
                  observer.clientSessionWillEnd(session);
                  return true;
              }
          });
      }
docs: Called by PresentsSession when it is about to end its session.