diff -r 000000000000 -r 6474c204b198 browser/base/content/test/general/browser_bug595507.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/general/browser_bug595507.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,39 @@
+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);
+}