gistfile1.js

// delay helper, for some reason they left out the clearTimeout in the B implementation
var cancellableDelay = function (ms) {
  var t;
  return new B(function(resolve,reject) {
    t = setTimeout(function() {
      resolve();
    }, ms);
  }).cancellable()
  .catch(B.CancellationError, function(e) {
    clearTimeout(t);
    throw e;
  });
};   


  let verify = async () => {
    this.pageLoadDelay = cancellableDelay(timeoutMs)
    try { await this.pageLoadDelay } catch(err) { if(err instanceof B.CancellationError) return; }
  
    let ready = await this.checkPageIsReady();
    // if we are ready, or we've spend too much time on this
    if (ready || (this.pageLoadMs > 0 && (start + this.pageLoadMs) < Date.now())) {
      log.debug('Page is ready');
      this.pageLoading = false;
     } else {
       log.debug('Page was not ready, retrying');
       await verify();
    }
  };
  
  await verify();
}

cancelPageLoad () {
  log.debug('Unregistering from page readiness notifications');
  this.pageLoading = false;
  this.pageLoadDelay.cancel();
}