Expose Durable Storage API to script

Source/modules/quota/NavigatorStorageQuota.idl

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 partial interface Navigator {
     [MeasureAs=PrefixedStorageQuota] readonly attribute DeprecatedStorageQuota webkitTemporaryStorage;
     [MeasureAs=PrefixedStorageQuota] readonly attribute DeprecatedStorageQuota webkitPersistentStorage;
 
     [RuntimeEnabled=QuotaPromise] readonly attribute StorageQuota storageQuota;
+    [RuntimeEnabled=DurableStorage] readonly attribute StorageManager storage;
 };