Issue 4864 - Start using ESLint for adblockpluschrome

ext/background.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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/>.
  */
 
 "use strict";
 
+(function()
 {
   let nonEmptyPageMaps = Object.create(null);
   let pageMapCounter = 0;
 
   let PageMap = ext.PageMap = function()
   {
     this._map = Object.create(null);
     this._id = ++pageMapCounter;
   };
   PageMap.prototype = {
@@ skipping 30 matching lines @@
     {
       this._delete(page.id);
     }
   };
 
   ext._removeFromAllPageMaps = pageId =>
   {
     for (let pageMapId in nonEmptyPageMaps)
       nonEmptyPageMaps[pageMapId]._delete(pageId);
   };
-}
+}());