cument.createElement("input");
      input.type = "hidden";
      input.name = "thereplacement";
      form.append(input);

      document.body.append(form);
      form.requestSubmit();
    };
  `;

  const startURL = "resources/code-injector.html?pipe=sub(none)&code=" + encodeURIComponent(code);
  const afterReplacementURL = "/common/blank.html?thereplacement=";
  const iframe = insertIframe(t, startURL);

  assert_equals(history.length, startingHistoryLength, "Inserting the under-test iframe must not chan