message: Handle content loading timeouts more gracefuly.
  This converts some errors that look like `Test run ended in failure: Error thrown outside of test function: Cannot read property 'WCT' of null`
  into ones that look like `Timed out loading http://localhost/:17604/components/my-component/test.html`
diff: @@ -127,6 +127,12 @@ export default class ChildRunner {
  loaded(error: any) {
  util.debug('ChildRunner#loaded', this.url, error);
  + if (this.iframe.contentWindow == null && error) {
  + this.signalRunComplete(error);
  + this.done();
  + return;
  + }
  +
  // Not all targets have WCT loaded (compatiblity mode)
  if (this.iframe.contentWindow.WCT) {
  this.share = this.iframe.contentWindow.WCT.share;
  