Revert of Adding strict mode for bookmark_manager file for better error checking.

chrome/browser/resources/bookmark_manager/js/main.js

Index: chrome/browser/resources/bookmark_manager/js/main.js
diff --git a/chrome/browser/resources/bookmark_manager/js/main.js b/chrome/browser/resources/bookmark_manager/js/main.js
index dea7bfb756b36c3eb7a04defe9005caaf307d9b3..c48bb1307b2782bc8e61b45a7aa7430d10dbd6c9 100644
--- a/chrome/browser/resources/bookmark_manager/js/main.js
+++ b/chrome/browser/resources/bookmark_manager/js/main.js
@@ -1,8 +1,6 @@
 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-
-'use strict';
 
 (function() {
 /** @const */ var BookmarkList = bmm.BookmarkList;