Issue 6956 - Move extension's style sheet generation into core

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 267 matching lines @@
 };
 
 exports.testCreateStyleSheet = function(test)
 {
   test.equal(
     createStyleSheet([
       "html", "#foo", ".bar", "#foo .bar", "#foo > .bar",
       "#foo[data-bar='bar']"
     ]),
     "html, #foo, .bar, #foo .bar, #foo > .bar, #foo[data-bar='bar'] " +
-    "{display: none !important;}",
+    "{display: none !important;}\n",
     "Style sheet creation should work"
   );
 
   let selectors = new Array(50000).map((element, index) => ".s" + index);
 
-  test.equal(createStyleSheet(selectors).split("\n").length,
+  test.equal((createStyleSheet(selectors).match(/\n/g) || []).length,
              Math.ceil(50000 / selectorGroupSize),
              "Style sheet should be split up into rules with at most " +
              selectorGroupSize + " selectors each");
 
   test.done();
 };