/**
  * Generates the button. Updates the literal field with the correct HTML
  * based on any post-contruct updates
  *    
  * @param array $attributes
  * @return SSViewer
  */
 public function FieldHolder($attributes = array())
 {
     if ($this->shouldDisplay()) {
         $this->setContent($this->getButtonHTML());
         return parent::FieldHolder($attributes);
     }
 }