The Tor Browser / file revision

 var gInvalidFormPopup = document.getElementById('invalid-form-popup');

 ok(gInvalidFormPopup,

    "The browser should have a popup to show when a form is invalid");

 /**

  * Make sure that the form validation error message shows even if the form is in an iframe.

  */

 function test()

 {

   waitForExplicitFinish();

   let uri = "data:text/html,<iframe src=\"data:text/html,<iframe name='t'></iframe><form target='t' action='data:text/html,'><input required id='i'><input id='s' type='submit'></form>\"</iframe>";

   let tab = gBrowser.addTab();

   gInvalidFormPopup.addEventListener("popupshown", function() {

     gInvalidFormPopup.removeEventListener("popupshown", arguments.callee, false);

     let doc = gBrowser.contentDocument.getElementsByTagName('iframe')[0].contentDocument;

     is(doc.activeElement, doc.getElementById('i'),

        "First invalid element should be focused");

     ok(gInvalidFormPopup.state == 'showing' || gInvalidFormPopup.state == 'open',

        "The invalid form popup should be shown");

     // Clean-up and next test.

     gBrowser.removeTab(gBrowser.selectedTab, {animate: false});

     executeSoon(finish);

   }, false);

   tab.linkedBrowser.addEventListener("load", function(aEvent) {

     tab.linkedBrowser.removeEventListener("load", arguments.callee, true);

     gBrowser.contentDocument.getElementsByTagName('iframe')[0].contentDocument

       .getElementById('s').click();

   }, true);

   gBrowser.selectedTab = tab;

   gBrowser.selectedTab.linkedBrowser.loadURI(uri);

 }