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

components/sync_driver/resources/sync_node_browser.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-node-browser-refresher {
   border-bottom: 1px rgb(160,160,160) solid;
 }
 
 #sync-node-browser-refresher > * {
   display: inline-block;
 }
 
 #sync-node-browser-container {
-  display: -webkit-box;
+  display: flex;
   height: 750px;
 }
 
 #sync-node-tree-container {
   -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;
+  min-width: 200px;
   overflow: auto;
   width: 200px;
 }
 
 #sync-node-tree {
   display: inline-block;
   min-width: 100%;
   overflow: visible; /* let the container do the scrolling */
 }
 
 /* TODO(akalin): Find a better icon to use for leaf nodes. */
 #sync-node-tree .leaf .tree-label {
   background-image: url(../../../ui/webui/resources/images/star_small.png);
 }
 
 #sync-node-splitter {
   background-color: rgb(235, 239, 249);
   cursor: col-resize;
-  width: 5px;
+  min-width: 5px;
 <if expr="is_win">
   /* TODO(akalin): Make the BMM also use this style. */
   cursor: e-resize;
 </if>
 }
 
 #sync-node-details-container {
-  -webkit-box-flex: 1;
+  flex: 1;
   height: 100%;
   overflow: auto;
   visibility: hidden;  /* Element is invisible until first refresh. */
 }
 
 #node-details {
-  width: 100%;
+  flex-grow: 1;
 }
 
 #node-details td {
   vertical-align: top;
   white-space: nowrap;
 }
 
 #node-details tr:nth-child(odd) {
   background: rgb(239, 243, 255);
 }