Issue 5735 - Use JS Map instead of Object for matcher properties filterByKeyword and keywordByFilter

test/filterListener.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present 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 46 matching lines @@
   callback();
 };
 
 function checkKnownFilters(test, text, expected)
 {
   let result = {};
   for (let type of ["blacklist", "whitelist"])
   {
     let matcher = defaultMatcher[type];
     let filters = [];
-    for (let keyword in matcher.filterByKeyword)
+    for (let [keyword, list] of matcher.filterByKeyword)
     {
-      let list = matcher.filterByKeyword[keyword];
       for (let i = 0; i < list.length; i++)
       {
         let filter = list[i];
         test.equal(matcher.getKeywordForFilter(filter), keyword,
                    "Keyword of filter " + filter.text);
         filters.push(filter.text);
       }
     }
     result[type] = filters;
   }
@@ skipping 240 matching lines @@
   checkKnownFilters(test, "disable exception rules", {blacklist: [filter1.text, filter3.text], whitelist: [filter2.text]});
 
   FilterStorage.removeSubscription(subscription4);
   checkKnownFilters(test, "remove subscription from the list", {blacklist: [filter1.text]});
 
   subscription3.disabled = false;
   checkKnownFilters(test, "enable exception rules", {blacklist: [filter1.text], whitelist: [filter2.text]});
 
   test.done();
 };