Convert Chromoting to use the new, non-deprecated flexbox

remoting/webapp/connection_history.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.
  */
 
 #connection-history-dialog {
   margin-top: -80px;
   height: 580px;
   width: 880px;
 }
 
 #connection-history-options {
   margin-top: 30px;
-  display: -webkit-box;
+  display: -webkit-flex;
 }
 
 #connection-history-scroller {
   margin-top: 30px;
   height: 370px;
   width: 100%;
   overflow: auto;
 }
 
 #connection-history-table {
@@ skipping 56 matching lines @@
   background-image: url('disclosure_arrow_down.webp');
 }
 
 .zippy {
   width: 30px;
   height: 11px;
   background-image: url('disclosure_arrow_right.webp');
   background-repeat: no-repeat;
   background-position: 10px 50%;
 }