Google Apps Script FileUpload() without FormPanel?
function doGet(e) {
  var app = UiApp.createApplication().setTitle("Upload CSV to Sheet");
  var form = app.createFormPanel().setId('frm').setEncoding('multipart/form-data');
  var formContent = app.createVerticalPanel();
  form.add(formContent);
  formContent.add(app.createFileUpload().setName('thefile'));
  formContent.add(app.createSubmitButton('Submit'));
  app.add(form);
  return app;
}

function doPost(e) {
  // data returned is a blob for FileUpload widget
  var fileBlob = e.parameter.thefile;
  var doc = DocsList.createFile(fileBlob);
  app.close();
  return app;
}

function doGet(e) {

  var app = UiApp.createApplication().setTitle("Upload CSV to Sheet");
  var formContent = app.createVerticalPanel();
  var submitServerHandler = app.createServerClickHandler('submitHandler_');
  formContent.add(app.createFileUpload().setName('thefile'));
  submitServerHandler.addCallbackElement(formContent);
  formContent.add(app.createButton('Submit').addClickHandler(submitServerHandler));
  app.add(formContent);
  return app;
}

function submitHandler_(e) {
  // data returned is a blob for FileUpload widget
  var fileBlob = e.parameter.thefile;
  var doc = DocsList.createFile(fileBlob);
  app.close();
  return app;
}