[Sync] chrome://sync-internals uses deprecated CSS

components/sync_driver/resources/sync_search.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. */
 
 #sync-search-query {
   width: 16em;
 }
 
 #sync-search-query[error] {
   background-color: rgb(255,170,170);
 }
 
 .sync-search-quicklink {
   background-color: rgb(239,243,255);
   padding-left: 10px;
   padding-right: 10px;
 }
 
 #sync-search-status {
   color: rgb(51,51,51);
   font-style: italic;
 }
 
 #sync-results-container {
-  display: -webkit-box;
+  display: flex;
   /* Should be > #sync-page's min-height. */
   /* TODO(akalin): Find a less hacky way to do this. */
   height: 750px;
 }
 
 #sync-results-list {
   -webkit-padding-start: 10px;
   box-sizing: border-box;
   height: 100%;
   /* min-width and max-width are used by the split pane. */
   max-width: 50%;
   min-width: 50px;
   overflow: auto;
   padding: 5px;
   width: 275px;
 }
 
 #sync-results-splitter {
   background-color: rgb(235, 239, 249);
   cursor: col-resize;
 <if expr="is_win">
   /* TODO(akalin): Make the BMM also use this style. */
   cursor: e-resize;
 </if>
   width: 5px;
 }
 
 #sync-result-details-container {
-  -webkit-box-flex: 1;
+  flex: 1;
   height: 100%;
   overflow: auto;
   /* TODO(akalin): Figure out why this is needed, even with box-flex: 1. */
   width: 100%;
 }