Of("/") + 1);
  switch (file) {
  case "constructors.html":
    return "parent window";
  case "constructors-support.html":
    return "child window";
  default:
    return "???";
  }
}

async_test(function() {
  var iframe = document.createElement("iframe");
  iframe.onload = this.step_func_done(function() {
    var child = iframe.contentWindow;
    test(function() {
      var dp = new DOMParser();
      assert_equals(Object.getPrototypeOf(dp), DOMParser.prototype);
      assert_equals(object_realm(dp), "p