Twenty Fourteen Multisite Activation and Sign up

twentyfourteen_ms.php

<?php

/**
 * Adds boddy class on Multisite Activation and Sign Up pages.
 * 
 */ 
function twentyfourteen_multisite_classes() {
	add_filter( 'body_class', 'twentyfourteen_add_multisite_classes' );
}
add_action( 'activate_header', 'twentyfourteen_multisite_classes' );
add_action( 'signup_header', 'twentyfourteen_multisite_classes' );

function twentyfourteen_add_multisite_classes( $classes ){
	$classes[] = 'multisite-activate-signup';
	return $classes;
}