diff -r 000000000000 -r 6474c204b198 dom/browser-element/mochitest/browserElement_BrowserWindowNamespace.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/browser-element/mochitest/browserElement_BrowserWindowNamespace.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,53 @@
+/* Any copyright is dedicated to the public domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+// Bug 780351 - Test that mozbrowser does /not/ divide the window name namespace.
+// Multiple mozbrowsers inside the same app are like multiple browser tabs;
+// they share a window name namespace.
+
+"use strict";
+
+SimpleTest.waitForExplicitFinish();
+browserElementTestHelpers.setEnabledPref(true);
+browserElementTestHelpers.addPermission();
+
+function runTest() {
+  var iframe1 = document.createElement('iframe');
+  SpecialPowers.wrap(iframe1).mozbrowser = true;
+
+  // Two mozbrowser frames with the same code both do the same
+  // window.open("foo", "bar") call.  We should only get one
+  // mozbrowseropenwindow event.
+
+  iframe1.addEventListener('mozbrowseropenwindow', function(e) {
+    ok(true, "Got first mozbrowseropenwindow event.");
+    document.body.appendChild(e.detail.frameElement);
+
+    e.detail.frameElement.addEventListener('mozbrowserlocationchange', function(e) {
+      if (e.detail == "http://example.com/#2") {
+        ok(true, "Got locationchange to http://example.com/#2");
+        SimpleTest.finish();
+      }
+      else {
+        ok(true, "Got locationchange to " + e.detail);
+      }
+    });
+
+    SimpleTest.executeSoon(function() {
+      var iframe2 = document.createElement('iframe');
+      SpecialPowers.wrap(iframe2).mozbrowser = true;
+
+      iframe2.addEventListener('mozbrowseropenwindow', function(e) {
+        ok(false, "Got second mozbrowseropenwindow event.");
+      });
+
+      document.body.appendChild(iframe2);
+      iframe2.src = 'file_browserElement_BrowserWindowNamespace.html#2';
+    });
+  });
+
+  document.body.appendChild(iframe1);
+  iframe1.src = 'file_browserElement_BrowserWindowNamespace.html#1';
+}
+
+addEventListener('testready', runTest);