Add down indicator to advanced menu in mobile

It is a dropdown list so give it the down indicator we use elsewhere.

Change-Id: I8976f2bc5edd1e221ca155da02660703318480ac

modules/ve-mw/init/targets/ve.init.mw.MobileArticleTarget.js

@@ -159,6 +159,7 @@ ve.init.mw.MobileArticleTarget.prototype.attachToolbarSaveButton = function () {
 		{
 			type: 'list',
 			icon: 'advanced',
+			indicator: 'down',
 			title: ve.msg( 'visualeditor-pagemenu-tooltip' ),
 			include: [ 'editModeSource' ]
 		}