Optmize filter list in elemHide.js for memory usage

lib/filterListener.js

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2014 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 122 matching lines @@
 
   TimeLine.leave("Filter listener initialization done");
 }
 init();
 
 /**
  * Calls ElemHide.apply() if necessary.
  */
 function flushElemHide()
 {
+  ElemHide.compact();
   if (!batchMode && ElemHide.isDirty)
     ElemHide.apply();
 }
 
 /**
  * Notifies Matcher instances or ElemHide object about a new filter
  * if necessary.
  * @param {Filter} filter filter that has been added
  */
 function addFilter(filter)
@@ skipping 115 matching lines @@
     defaultMatcher.clear();
     ElemHide.clear();
     for (let subscription of FilterStorage.subscriptions)
       if (!subscription.disabled)
         subscription.filters.forEach(addFilter);
     flushElemHide();
   }
   else if (action == "save")
     isDirty = 0;
 }