title: JS: Transfer DataTransferItemList to WebWorker
body: <p>i want to use the synchroneous JS FileSystem API, therefore, this code has to be put to a webworker. the incoming data for the webworker are taken from a dragndrop event (dataTransfer.items) in order to be able to use chromes newest capabilitiy to upload folders. 
  sadly, every try is canceled by chrome with a "Uncaught Error: DATA_CLONE_ERR: DOM Exception 25".</p>
  
  <p>basically, its like this:</p>
  
  <pre><code>  var files=e.dataTransfer.items; [copying the DataTransferItemList]
    var worker=new Worker(...)
    worker.postMessage(files);
  </code></pre>
  
  <p>this does not work. any idea, why?
  a similar (but not 100% identical) example can be found here: <a href="http://www.html5rocks.com/en/tutorials/file/filesystem-sync/">http://www.html5rocks.com/en/tutorials/file/filesystem-sync/</a> - this seems to work. its not a DataTransferItemList, its a FileList there - cant this type of List be serialized?</p>
  
  <p>Thanks,
  Christoph</p>