title: How to listen for child window closing?
body: <p>I am opening a child window for Facebook sharing this way:</p>
  <pre><code>window.open(sharingUrl,'','toolbar=0,status=0,width=626,height=436');
  </code></pre>
  <p>The window is automatically closed when a user clicks share or close...</p>
  <p>Is there a way to add a listener to these events?</p>