diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/private-browsing/window/utils.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/private-browsing/window/utils.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+'use strict';
+
+module.metadata = {
+  'stability': 'unstable'
+};
+
+const privateNS = require('../../core/namespace').ns();
+
+function getOwnerWindow(thing) {
+  try {
+    // check for and return associated window
+    let fn = (privateNS(thing.prototype) || privateNS(thing) || {}).getOwnerWindow;
+
+    if (fn)
+      return fn.apply(fn, [thing].concat(arguments));
+  }
+  // stuff like numbers and strings throw errors with namespaces
+  catch(e) {}
+  // default
+  return undefined;
+}
+getOwnerWindow.define = function(Type, fn) {
+  privateNS(Type.prototype).getOwnerWindow = fn;
+}
+
+getOwnerWindow.implement = function(instance, fn) {
+  privateNS(instance).getOwnerWindow = fn;
+}
+
+exports.getOwnerWindow = getOwnerWindow;