diff -r 000000000000 -r 6474c204b198 dom/browser-element/mochitest/browserElement_TargetTop.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/browser-element/mochitest/browserElement_TargetTop.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,31 @@
+/* Any copyright is dedicated to the public domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Bug 771273 - Check that window.open(url, '_top') works properly with <iframe
+// mozbrowser>.
+"use strict";
+
+SimpleTest.waitForExplicitFinish();
+browserElementTestHelpers.setEnabledPref(true);
+browserElementTestHelpers.addPermission();
+
+function runTest() {
+  var iframe = document.createElement('iframe');
+  SpecialPowers.wrap(iframe).mozbrowser = true;
+
+  iframe.addEventListener('mozbrowseropenwindow', function(e) {
+    ok(false, 'Not expecting an openwindow event.');
+  });
+
+  iframe.addEventListener('mozbrowserlocationchange', function(e) {
+    if (/file_browserElement_TargetTop.html\?2$/.test(e.detail)) {
+      ok(true, 'Got the locationchange we were looking for.');
+      SimpleTest.finish();
+    }
+  });
+
+  document.body.appendChild(iframe);
+  iframe.src = 'file_browserElement_TargetTop.html';
+}
+
+addEventListener('testready', runTest);