code: protected final void safePostMessage (
          final DownstreamMessage msg, final PresentsConnection expect)
      {
          _omgr.postRunnable(new Runnable() {
              public void run () {
                  postMessage(msg, expect);
              }
          });
      }
docs: Callable from non-dobjmgr thread, this queues up a runnable on the dobjmgr thread to post
  the supplied message to this client.