'primary', 'container' => '', 'items_wrap' => '', 'menu_class' => 'mdl-navigation primary-navigation', 'walker' => new Blog_Material_Walker_Nav_Menu() ]); ?> 'social', 'container' => '', 'items_wrap' => '', 'menu_class' => 'mdl-navigation social-navigation', 'walker' => new Blog_Material_Walker_Nav_Menu(), 'depth' => 1 ]); ?>