t.  It will never happen in a browser that obeys the
    // spec, so it's really just insurance.  I don't think it actually gets
    // hit by anything.
    iframe.contentDocument.appendChild(iframe.contentDocument.implementation.createDocumentType("html", "", ""));
  }
  iframe.contentDocument.appendChild(referenceDoc.documentElement.cloneNode(true));
  iframe.contentWindow.setupRangeTests();
  iframe.contentWindow.testRangeInput = testRanges[i];
  iframe.contentWindow.run();
}

function testCloneContents(