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

lib/subscriptionClasses.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 Definition of Subscription class and its subclasses.
  */
+
+"use strict";
 
 let {ActiveFilter, BlockingFilter, WhitelistFilter, ElemHideBase} = require("filterClasses");
 let {FilterNotifier} = require("filterNotifier");
 
 /**
  * Abstract base class for filter subscriptions
  *
  * @param {String} url    download location of the subscription
  * @param {String} [title]  title of the filter subscription
  * @constructor
@@ skipping 512 matching lines @@
     if (this.errors)
       buffer.push("errors=" + this.errors);
     if (this.version)
       buffer.push("version=" + this.version);
     if (this.requiredVersion)
       buffer.push("requiredVersion=" + this.requiredVersion);
     if (this.downloadCount)
       buffer.push("downloadCount=" + this.downloadCount);
   }
 };