title: FileTransfer onprogress not working - PhoneGap 3.5.0
body: <p>The <code>onprogress</code> event handler never seems to be called. The success callback comes through fine and the download works. Is there something I'm doing wrong here?</p>
  
  <pre><code>filesystem.root.getFile('/path/to/file', { create: true }, function (file) {
  
      var transfer = new FileTransfer();
  
      transfer.onprogress = function () {
          console.log(arguments);
      };
  
      transfer.download(
          'http://example.com/path/to/file',
          file.toURL(),
          function () { console.log('success'); },
          function () { console.log('error'); },
          true
      );
  
  }, function () { console.log('error'); });
  </code></pre>
  
  <p>The app uses PhoneGap 3.5.0 with the newest file and file-transfer plugins. I'm testing on an iPad with iOS 8.</p>