diff -r 000000000000 -r 6474c204b198 browser/modules/offlineAppCache.jsm
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/modules/offlineAppCache.jsm	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,20 @@
+/* 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/. */
+ 
+this.EXPORTED_SYMBOLS = ["OfflineAppCacheHelper"];
+
+Components.utils.import('resource://gre/modules/LoadContextInfo.jsm');
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+this.OfflineAppCacheHelper = {
+  clear: function() {
+    var cacheService = Cc["@mozilla.org/netwerk/cache-storage-service;1"].getService(Ci.nsICacheStorageService);
+    var appCacheStorage = cacheService.appCacheStorage(LoadContextInfo.default, null);
+    try {
+      appCacheStorage.asyncEvictStorage(null);
+    } catch(er) {}
+  }
+};