diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/tabs/tabs-firefox.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/tabs/tabs-firefox.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,68 @@
+/* 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';
+
+// TODO: BUG 792670 - remove dependency below
+const { browserWindows: windows } = require('../windows');
+const { tabs } = require('../windows/tabs-firefox');
+const { isPrivate } = require('../private-browsing');
+const { isWindowPBSupported } = require('../private-browsing/utils')
+const { isPrivateBrowsingSupported } = require('sdk/self');
+
+const supportPrivateTabs = isPrivateBrowsingSupported && isWindowPBSupported;
+
+function newTabWindow(options) {
+  // `tabs` option is under review and may be removed.
+  return windows.open({
+    tabs: [ options ],
+    isPrivate: options.isPrivate
+  });
+}
+
+Object.defineProperties(tabs, {
+  open: { value: function open(options) {
+    if (options.inNewWindow) {
+        newTabWindow(options);
+        return undefined;
+    }
+
+    let activeWindow = windows.activeWindow;
+    let privateState = (supportPrivateTabs && (options.isPrivate || isPrivate(activeWindow))) || false;
+
+    // if the active window is in the state that we need then use it
+    if (activeWindow && (!supportPrivateTabs || privateState === isPrivate(activeWindow))) {
+      activeWindow.tabs.open(options);
+    }
+    else {
+      // find a window in the state that we need
+      let window = getWindow(privateState);
+      if (window) {
+        window.tabs.open(options);
+      }
+      // open a window in the state that we need
+      else {
+        newTabWindow(options);
+      }
+    }
+
+    return undefined;
+  }}
+});
+
+function getWindow(privateState) {
+  for each (let window in windows) {
+    if (privateState === isPrivate(window)) {
+      return window;
+    }
+  }
+  return null;
+}
+
+// Workaround for bug 674195. Freezing objects from other compartments fail,
+// so we use `Object.freeze` from the same component as objects
+// `hasOwnProperty`. Since `hasOwnProperty` here will be from other component
+// we override it to support our workaround.
+module.exports = Object.create(tabs, {
+  isPrototypeOf: { value: Object.prototype.isPrototypeOf }
+});