title: jQuery.form uploadProgress never called
body: <p>I'm trying to write a WordPress plugin that uploads a video using the Vimeo API.  I am trying to provide a progress bar for the upload to the user can see that it is working.  To produce the status bar I am using the jQuery.Form plugin and accessing the uploadProgress callback but I cannot get the callback to fire. I am using Chrome 19 so the upload and file API's should be available to the browser.</p>
  
  <p>I have been copying the code from the jQuery.Form demo, which works on their page but has no effect on mine. - <a href="http://jquery.malsup.com/form/progress.html" rel="nofollow">http://jquery.malsup.com/form/progress.html</a></p>
  
  <p>The little Chrom notification in the bottom left of the screen is showing the upload percentage so I am confident that the file is being sent.</p>
  
  <p>Thoughts?</p>
  
  <pre><code>    &lt;form method="POST" action="&lt;?php echo $endpoint; ?&gt;" id="vimeo_upload_form" enctype="multipart/form-data"&gt;
          &lt;p&gt;
              &lt;label&gt;Upload video to Vimeo&lt;/label&gt;
              &lt;input type="hidden" name="ticket_id" value="&lt;?php echo $token; ?&gt;" id="ticket_id"/&gt;
              &lt;input type="hidden" name="chunk_id" value="0" id="chunk_id"/&gt;
              &lt;input type="file" name="file_data" id="file_data"/&gt;
          &lt;/p&gt;
          &lt;p&gt;
              &lt;input type="submit" name="" value="upload"&gt;
          &lt;/p&gt;
      &lt;/form&gt;
  
  jQuery(document).ready(function($) {
  
  status_msg = $("#status_msg")
  console.log(status_msg)
  percent = $("#percentage")
  bar = $("#bar")
  
  $('#vimeo_upload_form').ajaxForm({
      beforeSend: function() {
  
          status_msg.empty();
          var percentVal = '0%';
          bar.width(percentVal)
          percent.html(percentVal);
      },
      uploadProgress: function(event, position, total, percentComplete) {
          var percentVal = percentComplete + '%';
          bar.width(percentVal)
          percent.html(percentVal);
      },
      complete: function(xhr) {
          status_msg.html(xhr.responseText);
      }
  }); 
  });
  </code></pre>