Issue 2582 - Optimize loop in ElemHide.getSelectorsForDomain() for V8

lib/elemHide.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2015 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
@@ skipping 360 matching lines @@
     return (key in filterByKey ? filterByKey[key] : null);
   },
 
   /**
    * Returns a list of all selectors active on a particular domain (currently
    * used only in Chrome, Opera and Safari).
    */
   getSelectorsForDomain: function(/**String*/ domain, /**Boolean*/ specificOnly)
   {
     let result = [];
-    for (let key in filterByKey)
+    let keys = Object.keys(filterByKey);
+    for (let key of keys)
     {
       let filter = filterByKey[key];
       if (specificOnly && (!filter.domains || filter.domains[""]))
         continue;
 
       if (filter.isActiveOnDomain(domain) && !this.getException(filter, domain))
         result.push(filter.selector);
     }
     return result;
   }
 };