Issue 6727 - Use string rather than map for single-domain filters

lib/filterClasses.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 383 matching lines @@
 
   /**
    * Map containing domains that this filter should match on/not match
    * on or null if the filter should match on all domains
    * @type {?Map.<string,boolean>}
    */
   get domains()
   {
     // Despite this property being cached, the getter is called
     // several times on Safari, due to WebKit bug 132872
-    let prop = Object.getOwnPropertyDescriptor(this, "domains");
+    let prop = Object.getOwnPropertyDescriptor(this, "_domains");
     if (prop)
-      return prop.value;
+    {
+      let {value} = prop;
+      return typeof value == "string" ?
+               new Map([[value, true], ["", false]]) : value;
+    }
 
     let domains = null;
 
     if (this.domainSource)
     {
       let source = this.domainSource;
       if (!this.domainSourceIsUpperCase)
       {
         // RegExpFilter already have uppercase domains
         source = source.toUpperCase();
       }
       let list = source.split(this.domainSeparator);
       if (list.length == 1 && list[0][0] != "~")
       {
         // Fast track for the common one-domain scenario
-        domains = new Map([["", false], [list[0], true]]);
+        domains = list[0];
       }
       else
       {
         let hasIncludes = false;
         for (let i = 0; i < list.length; i++)
         {
           let domain = list[i];
           if (domain == "")
             continue;
 
@@ skipping 14 matching lines @@
 
           domains.set(domain, include);
         }
         if (domains)
           domains.set("", !hasIncludes);
       }
 
       this.domainSource = null;
     }
 
-    Object.defineProperty(this, "domains", {value: domains, enumerable: true});
+    Object.defineProperty(this, "_domains", {value: domains});
     return this.domains;
   },
 
   /**
    * Array containing public keys of websites that this filter should apply to
    * @type {?string[]}
    */
   sitekeys: null,
 
   /**
@@ skipping 631 matching lines @@
  */
 function ElemHideEmulationFilter(text, domains, selector)
 {
   ElemHideBase.call(this, text, domains, selector);
 }
 exports.ElemHideEmulationFilter = ElemHideEmulationFilter;
 
 ElemHideEmulationFilter.prototype = extend(ElemHideBase, {
   type: "elemhideemulation"
 });