title: :not(..) selector not working in an insertion point
body: <p>As mentionned in the title, I can't make a <em>:not</em> selector work with the <code>select</code> attribute of a insertion point.</p>
  
  <p>As it is shown here <a href="http://jsbin.com/lusof/1/edit" rel="nofollow">http://jsbin.com/lusof/1/edit</a> :</p>
  
  <ul>
  <li>the syntax works with a querySelector</li>
  <li>a similar node is accessible if nor selected with the <em>not</em> selector</li>
  </ul>
  
  <p>Did I missed something obvious ?</p>
  
  <p>Thanks for your answers</p>