<?php
/**
 *
 * Copyright © 2013-2017 Magento, Inc. All rights reserved.
 * See COPYING.txt for license details.
 */
namespace Magento\Catalog\Model\Layer\Search;

class FilterableAttributeList extends \Magento\Catalog\Model\Layer\Category\FilterableAttributeList
{
    /**
     * @param \Magento\Catalog\Model\ResourceModel\Product\Attribute\Collection $collection
     * @return \Magento\Catalog\Model\ResourceModel\Product\Attribute\Collection
     */
    protected function _prepareAttributeCollection($collection)
    {
        $collection->addIsFilterableInSearchFilter()
            ->addVisibleFilter();
        return $collection;
    }
}
