Fix NTP issue because of -webkit-flexbox -> -webkit-flex rename

chrome/browser/resources/ntp4/new_tab.css

 /* 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. */
 
 html {
   /* It's necessary to put this here instead of in body in order to get the
      background-size of 100% to work properly */
   height: 100%;
   overflow: hidden;
 }
@@ skipping 384 matching lines @@
 /* In trash mode, hide the menus and web store link. */
 #footer.showing-trash-mode #chrome-web-store-link,
 #footer.showing-trash-mode .menu-container {
   -webkit-transition-delay: 0;
   opacity: 0;
   visibility: hidden;
 }
 
 #footer .menu-container {
   -webkit-flex-align: center;
-  /* Put menus in a flexbox so the order can easily be swapped. */
-  display: -webkit-flexbox;
+  /* Put menus in a flexible box so the order can easily be swapped. */
+  display: -webkit-flex;
   height: 100%;
   margin: 0;
 }
 
 /* Put the recently closed menu to the left when it's not visible. */
 #recently-closed-menu-button.invisible {
   -webkit-flex-order: -1;
   visibility: hidden;
 }
 
 #other-sessions-menu-button.invisible {
   display: none;
 }
 
 .other-sessions-promo-message {
   display: none;
   padding: 0;
 }
 
 .other-sessions-promo-message:only-child {
   display: block;
 }
 
 .other-sessions-promo-message p {
   margin: 0;
 }