title: google.script.run and form with input type=file produce string "FileUpload" not a blob
body: <p>I use HTMLServices with <code>google.script.run</code> calls with form in args and i try to get the image from my form input file field and store it in my drive.</p>
  <p>I get the value of all the fields correctly except the photodata field.
  <code>photodata</code> contain the string &quot;FileUpload&quot; instead of a blob.</p>
  <p>I have tested with <code>.getBlob</code> for the same result.</p>
  <p>Server Side :</p>
  <pre><code>function setUsager(form) {
    var blob = form.photodata;
    Logger.log(Utilities.jsonStingify(blob);
    DriveApp.getFolderById('0B2DdOMvW2Q84N0s4a21LM05wbms').createFile(form.usagerId,blob);
    obj = new {};
    obj.photo = file.getUrl();
    return obj;
  }
  </code></pre>
  <p>on click Handler</p>
  <pre><code>  function onUsagerEditFormSubmit() {
      loading(true);
      var form = this.parentNode;
      google.script.run.withSuccessHandler(showUsager)
          .withFailureHandler(showError)
          .setUsager(form);      
     
    }
  </code></pre>
  <p>And the form :</p>
  <pre class="lang-html prettyprint-override"><code>&lt;form name=&quot;usager-edit&quot; id=&quot;usager-edit&quot; method='post' enctype=&quot;multipart/form-data&quot;&gt;
    &lt;div class=&quot;hidden&quot;&gt;
      &lt;input type=&quot;text&quot; name=&quot;type&quot; id=&quot;type&quot; value=&quot;USAGER&quot; readonly=&quot;readonly&quot; /&gt;
      &lt;input type=&quot;text&quot; name=&quot;usagerId&quot; id=&quot;usagerId&quot; readonly=&quot;readonly&quot; /&gt;
    &lt;/div&gt;
    &lt;div class=&quot;field-container&quot;&gt;      
      &lt;label for=&quot;nom&quot;&gt;Nom&lt;/label&gt;
      &lt;input type=&quot;text&quot; name=&quot;nom&quot; id=&quot;nom&quot;&gt;
    &lt;/div&gt;
    &lt;div class=&quot;field-container&quot;&gt;
      &lt;label for=&quot;prenom&quot;&gt;Prenom&lt;/label&gt;
      &lt;input type=&quot;text&quot; name=&quot;prenom&quot; id=&quot;prenom&quot;&gt;
    &lt;/div&gt;
    &lt;div class=&quot;field-container&quot;&gt;
      &lt;label for=&quot;photo&quot;&gt;Photo&lt;/label&gt;
      &lt;input class=&quot;file&quot; type=&quot;file&quot; name=&quot;photodata&quot; id=&quot;photodata&quot; accept='image/*'&gt;
      &lt;div id=&quot;prev-photo&quot; name=&quot;prev-photo&quot;&gt;&lt;/div&gt;
      &lt;div class=&quot;clear&quot;&gt;&lt;/div&gt;
    &lt;/div&gt;
    &lt;input class=&quot;myButton&quot; onClick=&quot;onUsagerEditFormSubmit&quot; type=&quot;button&quot; name=&quot;save&quot; id=&quot;save-button&quot; value=&quot;Sauvegarder&quot; /&gt;
  &lt;/form&gt;
  </code></pre>