Customize: Ensure a newly-added custom link nav menu item has the appropriate CSS class names.

For nav menu items of the `custom` type, their `object` should also be set to `custom`, so that the `menu-item-custom` class name will be added.

Props vishalkakadiya.
Fixes #37575.

Built from https://develop.svn.wordpress.org/trunk@38301


git-svn-id: http://core.svn.wordpress.org/trunk@38242 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/js/customize-nav-menus.js

@@ -446,7 +446,7 @@
 				'url': itemUrl.val(),
 				'type': 'custom',
 				'type_label': api.Menus.data.l10n.custom_label,
-				'object': ''
+				'object': 'custom'
 			};
 
 			this.currentMenuControl.addItemToMenu( menuItem );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7-alpha-38300';
+$wp_version = '4.7-alpha-38301';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.