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

test/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 53 matching lines @@
     result.push("type=comment");
   else if (filter instanceof ActiveFilter)
   {
     result.push("disabled=" + filter.disabled);
     result.push("lastHit=" + filter.lastHit);
     result.push("hitCount=" + filter.hitCount);
 
     let domains = [];
     if (filter.domains)
     {
-      for (let [domain, isIncluded] of filter.domains)
+      if (typeof filter.domains == "string")
       {
-        if (domain != "")
-          domains.push(isIncluded ? domain : "~" + domain);
+        domains.push(filter.domains);
+      }
+      else
+      {
+        for (let [domain, isIncluded] of filter.domains)
+        {
+          if (domain != "")
+            domains.push(isIncluded ? domain : "~" + domain);
+        }
       }
     }
     result.push("domains=" + domains.sort().join("|"));
 
     if (filter instanceof RegExpFilter)
     {
       result.push("regexp=" + filter.regexp.source);
       result.push("contentType=" + filter.contentType);
       result.push("matchCase=" + filter.matchCase);
 
@@ skipping 450 matching lines @@
     filterRelative.rewriteUrl("http://content.server/file/foo.txt?bar"),
     "http://content.server/file/foo.txt/disable"
   );
   test.equal(
     filterRelative.rewriteUrl("http://example.com/file/foo.txt?bar"),
     "http://example.com/file/foo.txt/disable"
   );
 
   test.done();
 };