code: public function run33Update()
  	{
  		$objLayout = $this->Database->query("SELECT id, framework FROM tl_layout WHERE framework!=''");
  
  		while ($objLayout->next())
  		{
  			$strFramework = '';
  			$tmp = StringUtil::deserialize($objLayout->framework);
  
  			if (!empty($tmp) && \is_array($tmp))
  			{
  				if (($key = array_search('layout.css', $tmp)) !== false)
  				{
  					array_insert($tmp, $key + 1, 'responsive.css');
  				}
  
  				$strFramework = serialize(array_values(array_unique($tmp)));
  			}
  
  			$this->Database->prepare("UPDATE tl_layout SET framework=? WHERE id=?")
  						   ->execute($strFramework, $objLayout->id);
  		}
  
  		// Add the "viewport" field (triggers the version 3.3 update)
  		$this->Database->query("ALTER TABLE `tl_layout` ADD `viewport` varchar(64) NOT NULL default ''");
  	}
docs: Version 3.3.0 update