The Tor Browser / file revision

 /* 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, components: { ID: parseUUID } } = require('chrome');

 const { generateUUID } = Cc['@mozilla.org/uuid-generator;1'].

                           getService(Ci.nsIUUIDGenerator);

 // Returns `uuid`. If `id` is passed then it's parsed to `uuid` and returned

 // if not then new one is generated.

 exports.uuid = function uuid(id) id ? parseUUID(id) : generateUUID()