WP_Customize_Nav_Menu_Location_Control
Customize Menu Location Control Class.
WordPress File wp-includes/customize/class-wp-customize-nav-menu-location-control.php
WP_Customize_Nav_Menu_Location_Control::render_content()
Render content just like a normal select control.
WP_Customize_Nav_Menu_Location_Control::to_json()
Refresh the parameters passed to JavaScript via JSON.