Issue 4125 - [emscripten] Convert filter classes to C++

lib/filterNotifier.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/>.
  */
 
 /**
  * @fileOverview This component manages listeners and calls them to distributes
  * messages about filter changes.
  */
 
+"use strict";
+
 /**
  * List of registered listeners
  * @type function[]
  */
 let listeners = [];
 
 /**
  * This class allows registering and triggering listeners for filter events.
  * @class
  */
@@ skipping 31 matching lines @@
    *                 "filter.disabled", "filter.hitCount", "filter.lastHit")
    * @param {Subscription|Filter} item item that the change applies to
    */
   triggerListeners: function(action, item, param1, param2, param3)
   {
     let list = listeners.slice();
     for (let listener of list)
       listener(action, item, param1, param2, param3);
   }
 };