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';

 const Cc = Components.classes;

 const Ci = Components.interfaces;

 // use ppmm to handle file-picker message.

 let ppmm = Cc['@mozilla.org/parentprocessmessagemanager;1']

              .getService(Ci.nsIMessageListenerManager);

 let pickResult = null;

 function processPickMessage(message) {

   let sender = message.target.QueryInterface(Ci.nsIMessageSender);

   // reply FilePicker's message

   sender.sendAsyncMessage('file-picked', pickResult);

   // notify caller

   sendAsyncMessage('file-picked-posted', { type: 'file-picked-posted' });

 }

 function updatePickResult(result) {

   pickResult = result;

   sendAsyncMessage('pick-result-updated', { type: 'pick-result-updated' });

 }

 ppmm.addMessageListener('file-picker', processPickMessage);

 // use update-pick-result to change the expected pick result.

 addMessageListener('update-pick-result', updatePickResult);