Symfony FormType <2.6 what is the >=2.6 way? Without needing OptionsResolverInterface?

MandatorType <2.6

<?php

namespace Dpanel\Bundle\AdminBundle\Forms;

use Cwd\GenericBundle\Doctrine\EntityRepository;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use JMS\DiExtraBundle\Annotation as DI;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

/**
 * Class Mandator Form
 *
 * @package Dpanel\Bundle\AdminBundle\Forms
 * @author  Ludwig Ruderstaller <lr@cwd.at>
 *
 * @DI\Service("dpanel_admin_form_mandator")
 * @DI\Tag("form.type")
 */
class MandatorType extends AbstractType
{
    /**
     * @param FormBuilderInterface $builder
     * @param array                $options
     *
     * @return misc
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('foo', 'text', array('label' => 'Foobar'))
            ->add('save', 'submit', array('label' => 'Save'));
    }

    /**
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'validation_groups' => array('default'),
            'data_class' => 'Dpanel\Model\Entity\Mandator',
        ));
    }

    /**
     * @return string
     */
    public function getName()
    {
        return 'dpanel_admin_form_mandator';
    }
}

OptionsResolverInterface needs to stay in the method signature. That will change in 3.0.