Remove -webkit-*-before/after in:

chrome/browser/resources/chromeos/login/oobe_screen.css

 /* Copyright 2013 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.
  *
  * This contains common styling for all the OOBE screens.
  */
 
 .step {
   box-sizing: border-box;
   position: absolute;
@@ skipping 110 matching lines @@
 
 #security-info a:focus,
 #eula a:focus,
 .step-extra-controls a:focus {
   -webkit-transition: outline-color 200ms;
   /* Note: May use 1px solid here. */
   outline-color: rgb(77, 144, 254);
 }
 
 .step-extra-controls > *:not(:first-child) {
-  -webkit-margin-before: 7px;
+  margin-top: 7px;
 }
 
 html[dir=rtl] .step-extra-controls {
   left: auto;
   right: 49px;
 }
 
 #oobe.autolaunch #autolaunch-confirm-button,
 #oobe.autolaunch #autolaunch-cancel-button,
 #oobe.connect #continue-button,
@@ skipping 29 matching lines @@
 
 html[highlight=strong] #security-info a:focus,
 html[highlight=strong] #eula a:focus,
 html[highlight=strong] .step-extra-controls a:focus,
 html[highlight=strong] .menu-control:focus,
 html[highlight=strong] input[type='button']:focus,
 html[highlight=strong] button:focus {
   box-shadow: 0 0 23px rgb(77, 144, 254) !important;
 }