<!DOCTYPE HTML>
<html data-expando-prop="xyz">
<!--
https://bugzilla.mozilla.org/show_bug.cgi?id=874758
-->
<head>
  <meta charset="utf-8">
  <title>Test for Bug 874758</title>
  <script src="/tests/SimpleTest/SimpleTest.js"></script>
  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css"/>
  <script type="application/javascript">

  /** Test for Bug 874758 **/
  Object.prototype.expandoProp = 5;
  is({}.expandoProp, 5, "Should see this on random objects");

  is(document.head.dataset.expandoProp, 5, "Should see this on dataset too");
  is(document.documentElement.dataset.expandoProp, "xyz",
     "But if the dataset has it, we should get it from there");
  </script>
</head>
<body>
<a target="_blank" href="https://bugzilla.mozilla.org/show_bug.cgi?id=874758">Mozilla Bug 874758</a>
<p id="display"></p>
<div id="content" style="display: none">

</div>
<pre id="test">
</pre>
</body>
</html>
