add_shortcode( 'row', 'row_cb' );
function row_cb( $atts, $content = null ) {             
        $output = '';
        $output .= '<div class="row">';
        $output .= do_shortcode( $content );        
        $output .= '</div>';

        return $output; 
}

add_shortcode( 'col', 'col_cb' );
function col_cb( $atts, $content = null ) {     
    extract( shortcode_atts( array(
            'size'  => '',
        ), $atts ) );


    $output = '';
    $output .= '<div class="col">';
    $output .= do_shortcode( $content );        
    $output .= '</div>';

    return $output; 
}