Issue 4795 - Use modern JavaScript syntax

lib/messaging.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus 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 General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 /** @module messaging */
 
 "use strict";
 
-let {EventEmitter} = require("events");
+const {EventEmitter} = require("events");
 
 /**
  * Communication port wrapping ext.onMessage to receive messages.
  *
  * @constructor
  */
 function Port()
 {
   this._eventEmitter = new EventEmitter();
   this._onMessage = this._onMessage.bind(this);
@@ skipping 89 matching lines @@
 exports.getPort = function(window)
 {
   let port = new Port();
   window.addEventListener("unload", () =>
   {
     port.disconnect();
   });
   return port;
 };