Issue 6955 - Avoid making copies of common selector list

test/elemHide.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 255 matching lines @@
   test.equal(filtersByDomain.size, 2);
 
   ElemHide.remove(Filter.fromText("example.com##test"));
   test.equal(filtersByDomain.size, 2);
 
   ElemHide.remove(Filter.fromText("example.com,~www.example.com##test"));
   test.equal(filtersByDomain.size, 0);
 
   test.done();
 };
+
+exports.testGenericSelectorDedup = function(test)
+{
+  ElemHide.add(Filter.fromText("##test1"));
+  ElemHide.add(Filter.fromText("##test2"));
+  ElemHide.add(Filter.fromText("##test3"));
+
+  test.equal(ElemHide.getSelectorsForDomain("foo.example.com"),
+             ElemHide.getSelectorsForDomain("bar.example.com"));
+
+  ElemHide.add(Filter.fromText("foo.example.com##test4"));
+
+  test.notEqual(ElemHide.getSelectorsForDomain("foo.example.com"),
+                ElemHide.getSelectorsForDomain("bar.example.com"));
+
+  ElemHide.remove(Filter.fromText("foo.example.com##test4"));
+
+  test.equal(ElemHide.getSelectorsForDomain("foo.example.com"),
+             ElemHide.getSelectorsForDomain("bar.example.com"));
+
+  ElemHide.remove(Filter.fromText("##test1"));
+  ElemHide.remove(Filter.fromText("##test2"));
+  ElemHide.remove(Filter.fromText("##test3"));
+
+  test.equal(ElemHide.getSelectorsForDomain("foo.example.com"),
+             ElemHide.getSelectorsForDomain("bar.example.com"));
+
+  test.done();
+};