Remove -webkit-*-before/after in:

ui/login/screen_container.css

 /* Copyright 2014 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.
  */
 
 #outer-container {
   -webkit-box-align: center;
   -webkit-box-pack: center;
   -webkit-perspective: 1px; /* Workaround, see http://crbug.com/360567 */
   bottom: 51px;  /* Leave space for the header bar */
@@ skipping 88 matching lines @@
 
 #step-logo {
   -webkit-margin-start: 17px;
   display: -webkit-box;
   position: absolute;
   top: 15px;
 }
 
 #progress-dots {
   -webkit-box-pack: center;
-  -webkit-margin-before: 15px;
   -webkit-transition: opacity 200ms ease-in-out,
                       visibility 200ms ease-in-out;
   display: -webkit-box;
+  margin-top: 15px;
 }
 
 /* Hidden for the duration of initial transition. */
 .oobe-display #progress-dots.down {
   visibility: hidden;
 }
 
 .progdot {
   -webkit-margin-end: 12px;
   background: white;
@@ skipping 80 matching lines @@
   line-height: 31px;
   text-transform: lowercase;
   width: 23em;
 }
 
 .header-section::before {
   /* Divider in header between product name and title,
    * like "[Product name] > [step header]". */
   content: '\00A0\203A\00A0\00A0';
 }