Move 'use strict' to file level

Change-Id: I1f0dae4aa168e77c112bcd3688c98b84e4ce5f36
diff --git a/dev/js/src/hint/item.js b/dev/js/src/hint/item.js
index 80ac78b..2fcecee 100644
--- a/dev/js/src/hint/item.js
+++ b/dev/js/src/hint/item.js
@@ -1,6 +1,8 @@
 /**
  * Hint menu item based on MenuItem
  */
+"use strict";
+
 define(['menu/item', 'util'], function (itemClass) {
   return {