Issue 6564 - Replace desc and extend with __proto__

lib/subscriptionClasses.js

Index: lib/subscriptionClasses.js
===================================================================
--- a/lib/subscriptionClasses.js
+++ b/lib/subscriptionClasses.js
@@ -19,17 +19,16 @@
 
 /**
  * @fileOverview Definition of Subscription class and its subclasses.
  */
 
 const {ActiveFilter, BlockingFilter,
        WhitelistFilter, ElemHideBase} = require("./filterClasses");
 const {FilterNotifier} = require("./filterNotifier");
-const {desc, 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
  */
@@ -235,17 +234,19 @@
  * @augments Subscription
  */
 function SpecialSubscription(url, title)
 {
   Subscription.call(this, url, title);
 }
 exports.SpecialSubscription = SpecialSubscription;
 
-SpecialSubscription.prototype = extend(Subscription, {
+SpecialSubscription.prototype = {
+  __proto__: Subscription.prototype,
+
   /**
    * Filter types that should be added to this subscription by default
    * (entries should correspond to keys in SpecialSubscription.defaultsMap).
    * @type {string[]}
    */
   defaults: null,
 
   /**
@@ -282,23 +283,24 @@
         this.defaults.filter(
           type => type in SpecialSubscription.defaultsMap
         ).join(" ")
       );
     }
     if (this._lastDownload)
       buffer.push("lastDownload=" + this._lastDownload);
   }
-});
+};
 
-SpecialSubscription.defaultsMap = Object.create(null, desc({
+SpecialSubscription.defaultsMap = {
+  __proto__: null,
   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)
 {
@@ -339,17 +341,19 @@
  * @augments Subscription
  */
 function RegularSubscription(url, title)
 {
   Subscription.call(this, url, title || url);
 }
 exports.RegularSubscription = RegularSubscription;
 
-RegularSubscription.prototype = extend(Subscription, {
+RegularSubscription.prototype = {
+  __proto__: Subscription.prototype,
+
   _homepage: null,
   _lastDownload: 0,
 
   /**
    * Filter subscription homepage if known
    * @type {string}
    */
   get homepage()
@@ -396,58 +400,62 @@
   serialize(buffer)
   {
     Subscription.prototype.serialize.call(this, buffer);
     if (this._homepage)
       buffer.push("homepage=" + this._homepage);
     if (this._lastDownload)
       buffer.push("lastDownload=" + this._lastDownload);
   }
-});
+};
 
 /**
  * Class for filter subscriptions updated externally (by other extension)
  * @param {string} url    see Subscription()
  * @param {string} [title]  see Subscription()
  * @constructor
  * @augments RegularSubscription
  */
 function ExternalSubscription(url, title)
 {
   RegularSubscription.call(this, url, title);
 }
 exports.ExternalSubscription = ExternalSubscription;
 
-ExternalSubscription.prototype = extend(RegularSubscription, {
+ExternalSubscription.prototype = {
+  __proto__: RegularSubscription.prototype,
+
   /**
    * See Subscription.serialize()
    * @inheritdoc
    */
   serialize(buffer)
   {
     throw new Error(
       "Unexpected call, external subscriptions should not be serialized"
     );
   }
-});
+};
 
 /**
  * Class for filter subscriptions updated externally (by other extension)
  * @param {string} url  see Subscription()
  * @param {string} [title]  see Subscription()
  * @constructor
  * @augments RegularSubscription
  */
 function DownloadableSubscription(url, title)
 {
   RegularSubscription.call(this, url, title);
 }
 exports.DownloadableSubscription = DownloadableSubscription;
 
-DownloadableSubscription.prototype = extend(RegularSubscription, {
+DownloadableSubscription.prototype = {
+  __proto__: RegularSubscription.prototype,
+
   _downloadStatus: null,
   _lastCheck: 0,
   _errors: 0,
 
   /**
    * Status of the last download (ID of a string)
    * @type {string}
    */
@@ -566,9 +574,9 @@
       buffer.push("errors=" + this.errors);
     if (this.version)
       buffer.push("version=" + this.version);
     if (this.requiredVersion)
       buffer.push("requiredVersion=" + this.requiredVersion);
     if (this.downloadCount)
       buffer.push("downloadCount=" + this.downloadCount);
   }
-});
+};