Index: wp-includes/class-walker-nav-menu.php
===================================================================
--- wp-includes/class-walker-nav-menu.php	(revision 38433)
+++ wp-includes/class-walker-nav-menu.php	(working copy)
@@ -90,6 +90,12 @@
 		$classes = empty( $item->classes ) ? array() : (array) $item->classes;
 		$classes[] = 'menu-item-' . $item->ID;
 
+		if ( ( -1 === $args->depth ) || ( $args->depth > 0 && ( ( $depth + 1 ) === $args->depth ) ) ) {
+			$_classes = array_fill_keys( $classes, '' );
+			unset( $_classes['menu-item-has-children'] );
+			$classes = array_keys( $_classes );
+		}
+
 		/**
 		 * Filters the arguments for a single nav menu item.
 		 *