docs: function() {
      var self = this;
      // Pretend that there's another poll scheduled (which will prevent
      // _ensurePollIsScheduled from queueing any more polls).
      ++self._pollsScheduledButNotStarted;
      // Now block until all currently running or scheduled polls are done.
      self._taskQueue.runTask(function() {});
  
      // Confirm that there is only one "poll" (the fake one we're pretending to
      // have) scheduled.
      if (self._pollsScheduledButNotStarted !== 1)
        throw new Error("_pollsScheduledButNotStarted is " +
                        self._pollsScheduledButNotStarted);
    }