diff -r 000000000000 -r 6474c204b198 addon-sdk/source/lib/sdk/private-browsing/utils.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/addon-sdk/source/lib/sdk/private-browsing/utils.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,104 @@
+/* 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 { Cc, Ci, Cu } = require('chrome');
+const { defer } = require('../lang/functional');
+const { emit, on, once, off } = require('../event/core');
+const { when: unload } = require('../system/unload');
+const events = require('../system/events');
+const { deprecateFunction } = require('../util/deprecate');
+const { isOneOf, is, satisfiesVersion, version } = require('../system/xul-app');
+const { isWindowPrivate } = require('../window/utils');
+const { isPrivateBrowsingSupported } = require('../self');
+
+let deferredEmit = defer(emit);
+let pbService;
+let PrivateBrowsingUtils;
+
+// Private browsing is only supported in Fx
+if (isOneOf(['Firefox', 'Fennec'])) {
+  // get the nsIPrivateBrowsingService if it exists
+  try {
+    pbService = Cc["@mozilla.org/privatebrowsing;1"].
+                getService(Ci.nsIPrivateBrowsingService);
+
+    // a dummy service exists for the moment (Fx20 atleast), but will be removed eventually
+    // ie: the service will exist, but it won't do anything and the global private browing
+    //     feature is not really active.  See Bug 818800 and Bug 826037
+    if (!('privateBrowsingEnabled' in pbService))
+      pbService = undefined;
+  }
+  catch(e) { /* Private Browsing Service has been removed (Bug 818800) */ }
+
+  try {
+    PrivateBrowsingUtils = Cu.import('resource://gre/modules/PrivateBrowsingUtils.jsm', {}).PrivateBrowsingUtils;
+  }
+  catch(e) { /* if this file DNE then an error will be thrown */ }
+}
+
+// checks that global private browsing is implemented
+let isGlobalPBSupported = exports.isGlobalPBSupported = !!pbService && is('Firefox');
+
+// checks that per-window private browsing is implemented
+let isWindowPBSupported = exports.isWindowPBSupported =
+                          !pbService && !!PrivateBrowsingUtils && is('Firefox');
+
+// checks that per-tab private browsing is implemented
+let isTabPBSupported = exports.isTabPBSupported =
+                       !pbService && !!PrivateBrowsingUtils && is('Fennec') && satisfiesVersion(version, '>=20.0*');
+
+exports.isPermanentPrivateBrowsing = function() {
+ return !!(PrivateBrowsingUtils && PrivateBrowsingUtils.permanentPrivateBrowsing);
+}
+                       
+function ignoreWindow(window) {
+  return !isPrivateBrowsingSupported && isWindowPrivate(window) && !isGlobalPBSupported;
+}
+exports.ignoreWindow = ignoreWindow;
+
+function onChange() {
+  // Emit event with in next turn of event loop.
+  deferredEmit(exports, pbService.privateBrowsingEnabled ? 'start' : 'stop');
+}
+
+// Currently, only Firefox implements the private browsing service.
+if (isGlobalPBSupported) {
+  // set up an observer for private browsing switches.
+  events.on('private-browsing-transition-complete', onChange);
+}
+
+// We toggle private browsing mode asynchronously in order to work around
+// bug 659629.  Since private browsing transitions are asynchronous
+// anyway, this doesn't significantly change the behavior of the API.
+let setMode = defer(function setMode(value) {
+  value = !!value;  // Cast to boolean.
+
+  // default
+  return pbService && (pbService.privateBrowsingEnabled = value);
+});
+exports.setMode = deprecateFunction(
+  setMode,
+  'require("sdk/private-browsing").activate and ' +
+  'require("sdk/private-browsing").deactivate ' +
+  'are deprecated.'
+);
+
+let getMode = function getMode(chromeWin) {
+  if (isWindowPrivate(chromeWin))
+    return true;
+
+  // default
+  return pbService ? pbService.privateBrowsingEnabled : false;
+};
+exports.getMode = getMode;
+
+exports.on = on.bind(null, exports);
+
+// Make sure listeners are cleaned up.
+unload(function() off(exports));