public function getHtmlHeadEntrySet()
    {
        $set = parent::getHtmlHeadEntrySet();

        if ($this->tile !== null) {
            $set->addEntrySet($this->tile->getHtmlHeadEntrySet());
        }

        foreach ($this->groups as $group) {
            $set->addEntrySet($group->getHtmlHeadEntrySet());
        }

        return $set;
    }