Remove -webkit-*-before/after in:

chrome/browser/resources/chromeos/login/screen_error_message.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.
  */
 
 #error-message {
   width: 650px;
 }
 
 .show-with-ui-state-update,
@@ skipping 40 matching lines @@
   /* A hack used to prevent aliasing on High-DPI displays. */
   -webkit-transform: scale3d(1,1,1);
   background-clip: padding-box;
   background-color: white;
   border-bottom: 1px solid rgb(238,238,238);
   padding: 71px 20px 50px;
   text-align: center;
 }
 
 .error-icon {
-  -webkit-margin-after: 40px;
   height: 64px;
+  margin-bottom: 40px;
 }
 
 .error-title {
   color: #606060;
   font-size: 15px;
 }
 
 .error-body {
   background-color: rgb(249,249,249);
   padding: 20px 20px 20px;
 }
 
 .error-controls {
   background-color: rgb(249,249,249);
   padding: 20px 20px 20px;
 }
 
 .error-message-paragraph {
   font-size: 12px;
   line-height: 18px;
 }
 
 .error-message-paragraph {
-  -webkit-margin-before: 20px;
+  margin-top: 20px;
 }
 
 .error-message-paragraph a {
   color: rgb(17,85,204);
   text-decoration: none;
 }
 
 #offline-network-control {
   -webkit-align-items: center;
   display: -webkit-flex;
@@ skipping 35 matching lines @@
   -webkit-animation: connecting-indicator-ellipsis 3s 0 infinite;
 }
 
 #connecting-indicator-ellipsis-2 {
   -webkit-animation: connecting-indicator-ellipsis 3s 500ms infinite;
 }
 
 #connecting-indicator-ellipsis-3 {
   -webkit-animation: connecting-indicator-ellipsis 3s 1s infinite;
 }