onst testSubresource =
  async_test("A subresource fetched from an about:blank iframe is fetched " +
             "with no 'Referer' header");

window.addEventListener("message", msg => {
  const test_name = msg.data.test;
  const referrer = msg.data.referrer;
  if (test_name === "testFetchClientReferrer") {
    testFetchClientReferrer.step_func_done(() => {
      // Because the URL of the Document of <iframe src="about:blank"> is
      // "about:blank", the stripped URL is no referrer:
      // https://w3c