testShowForNewLinkWithDiffAppWindow() {
    const frame = dom.createDom(TagName.IFRAME);
    safe.setIframeSrc(
        frame, TrustedResourceUrl.fromConstant(Const.from('about:blank')));
    try {
      document.body.appendChild(frame);
      this.testShowForNewLink(frame.contentDocument);
    } finally {
      dom.removeNode(frame);
    }
  }
Fakes that the mock field is using an iframe and does the same test as
testShowForNewLink().
@suppress {strictMissingProperties} suppression added to enable type
checking