Google + Share button callback issue

Question

I'm trying to create a G+ Share button that 'onendinteraction' return 'confirm' if the user shared the link successfully. I've tried it with no success. When I log the user activity throught 'onendinteraction' event, it ever returns me 'hover' and never return me 'confirm', even if a user shared rightly the link.

Here is the code I've created, it's quite simple: http://codepen.io/anon/pen/DdjAo

<div class="g-plus" data-action="share" data-annotation="none" data-onendinteraction="googleEventShare" data-href="http://codepen.io/"></div>

        <script type="text/javascript">
          window.___gcfg = {lang: 'en'};

          (function() {
            var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true;
            po.src = 'https://apis.google.com/js/plusone.js';
            var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s);
          })();
        </script>


<script>
   function googleEventShare(params) {
     console.log(params.type);
   }
</script>