code: function startPoller(interval, setTimeout) {
      (function check() {
        forEach(pollFns, function(pollFn) { pollFn(); });
        pollTimeout = setTimeout(check, interval);
      })();
    }
docs: @param {number} interval How often should browser call poll functions (ms)
  @param {function()} setTimeout Reference to a real or fake `setTimeout` function.
  
  @description
  Configures the poller to run in the specified intervals, using the specified
  setTimeout fn and kicks it off.