code: @EventThread
      protected void clientSessionDidEnd (final PresentsSession session)
      {
          // notify the observers that the session is ended
          _clobservers.apply(new ObserverList.ObserverOp<ClientObserver>() {
              public boolean apply (ClientObserver observer) {
                  observer.clientSessionDidEnd(session);
                  return true;
              }
          });
      }
docs: Called by PresentsSession when it has ended its session.