title: downloadAsFile (google's Content Service) is not working
body: <p>I'm trying to use Google script's Content Service to export information from spreadsheet to XML file. The code looks like this:</p>
  
  <pre><code>function makeXML() {
      var StringToXML = "&lt;tag&gt;&lt;/tag&gt;";
      var output = ContentService.createTextOutput();
      output.setMimeType(ContentService.MimeType.XML);
      output.setContent(StringToXML);
      output.downloadAsFile("f.xml");
  }
  </code></pre>
  
  <p>When I launch this function - nothing happens. Though there are no errors so the function is running ok. Also when I'm trying to debug it by placing msgboxes in some lines (for example by getting content of output and messaging it) everything looks fine. Except <code>downloadAsFile</code>.</p>
  
  <p>I've also tried not setting mime type (default is TEXT) but still <code>downloadAsFile</code> is not working. Tried Google Chrome, Firefox. </p>
  
  <p>How to make it work?</p>