Issue 3538 - Filter listener tests fail for CSS property rules

lib/cssRules.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 CSS property filtering implementation.
  */
 
 let {ElemHide} = require("elemHide");
 let {Filter} =  require("filterClasses");
 
-let filters = Object.create(null);
+var filters = Object.create(null);
 
 /**
  * CSS rules component
  * @class
  */
 let CSSRules = exports.CSSRules =
 {
   /**
    * Removes all known filters
    */
@@ skipping 31 matching lines @@
     let keys = Object.getOwnPropertyNames(filters);
     for (let key of keys)
     {
       let filter = Filter.fromText(key);
       if (filter.isActiveOnDomain(domain) && !ElemHide.getException(filter, domain))
         result.push(filter);
     }
     return result;
   }
 };