Update managed icon in CrOS proxy settings dialog.

chrome/browser/resources/uber/uber_shared.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. */
 
 body.uber-frame {
   -webkit-margin-start: 155px;
   color: rgb(48, 57, 66);
 }
 
 html[dir='rtl'] body.uber-frame {
@@ skipping 148 matching lines @@
 
 .page-banner .page-banner-gradient {
   -webkit-margin-end: 20px;
   -webkit-margin-start: 0;
   margin-bottom: 9px;
 }
 
 .page-banner-text {
   -webkit-padding-end: 8px;
   -webkit-padding-start: 26px;
-  background-image: url('chrome://theme/IDR_MANAGED');
+  background-image: url('chrome://theme/IDR_CONTROLLED_SETTING_MANDATORY');
   background-position: 5px center;
   background-repeat: no-repeat;
   background-size: 16px;
   display: block;
   padding-bottom: 8px;
   padding-top: 8px;
 }
 
 .page-banner.clickable:active .page-banner-text {
   background: -webkit-linear-gradient(rgb(250, 230, 145),
                                       rgb(255, 242, 183));
 }