Issue 6559 - Change SpecialSubscription.defaultsMap to Map object

lib/subscriptionClasses.js

Index: lib/subscriptionClasses.js
===================================================================
--- a/lib/subscriptionClasses.js
+++ b/lib/subscriptionClasses.js
@@ -19,17 +19,17 @@
 
 /**
  * @fileOverview Definition of Subscription class and its subclasses.
  */
 
 const {ActiveFilter, BlockingFilter,
        WhitelistFilter, ElemHideBase} = require("./filterClasses");
 const {FilterNotifier} = require("./filterNotifier");
-const {desc, extend} = require("./coreUtils");
+const {extend} = require("./coreUtils");
 
 /**
  * Abstract base class for filter subscriptions
  *
  * @param {string} url    download location of the subscription
  * @param {string} [title]  title of the filter subscription
  * @constructor
  */
@@ -255,17 +255,17 @@
    * @return {boolean}
    */
   isDefaultFor(filter)
   {
     if (this.defaults && this.defaults.length)
     {
       for (let type of this.defaults)
       {
-        if (filter instanceof SpecialSubscription.defaultsMap[type])
+        if (filter instanceof SpecialSubscription.defaultsMap.get(type))
           return true;
         if (!(filter instanceof ActiveFilter) && type == "blacklist")
           return true;
       }
     }
 
     return false;
   },
@@ -276,30 +276,30 @@
    */
   serialize(buffer)
   {
     Subscription.prototype.serialize.call(this, buffer);
     if (this.defaults && this.defaults.length)
     {
       buffer.push("defaults=" +
         this.defaults.filter(
-          type => type in SpecialSubscription.defaultsMap
+          type => SpecialSubscription.defaultsMap.has(type)
         ).join(" ")
       );
     }
     if (this._lastDownload)
       buffer.push("lastDownload=" + this._lastDownload);
   }
 });
 
-SpecialSubscription.defaultsMap = Object.create(null, desc({
-  whitelist: WhitelistFilter,
-  blocking: BlockingFilter,
-  elemhide: ElemHideBase
-}));
+SpecialSubscription.defaultsMap = new Map([
+  ["whitelist", WhitelistFilter],
+  ["blocking", BlockingFilter],
+  ["elemhide", ElemHideBase]
+]);
 
 /**
  * Creates a new user-defined filter group.
  * @param {string} [title]  title of the new filter group
  * @return {SpecialSubscription}
  */
 SpecialSubscription.create = function(title)
 {
@@ -316,19 +316,19 @@
  * This group will act as the default group for this filter type.
  * @param {Filter} filter
  * @return {SpecialSubscription}
  */
 SpecialSubscription.createForFilter = function(filter)
 {
   let subscription = SpecialSubscription.create();
   subscription.filters.push(filter);
-  for (let type in SpecialSubscription.defaultsMap)
+  for (let [type, class_] of SpecialSubscription.defaultsMap)
   {
-    if (filter instanceof SpecialSubscription.defaultsMap[type])
+    if (filter instanceof class_)
       subscription.defaults = [type];
   }
   if (!subscription.defaults)
     subscription.defaults = ["blocking"];
   return subscription;
 };
 
 /**