title: DFP post-rendering callback
body: <p>I need to trigger some JavaScript <strong>after</strong> DFP has finished rendering all the ads on the page - or at least when it has triggered <em>collapseEmptyDivs</em> (which hides ad units that contain no line items).</p>
  
  <p>Is anyone aware of a way to get DFP to trigger a callback after either of these events?</p>