Remove -webkit-*-before/after in:

chrome/browser/resources/chromeos/login/oobe_screen_user_image.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.
  */
 
 #user-image {
   min-height: 443px;
   padding: 70px 17px 21px;
   width: 702px;
 }
 
 #user-image.loading {
   min-height: 609px; /* Should be the same as #gaia-signin height. */
   width: 722px; /* Should be the same as #gaia-signin width. */
 }
 
 #user-image-screen-curtain {
   -webkit-margin-start: 8px;
 }
 
 #user-image-screen-description {
-  -webkit-margin-before: 0;
+  margin-top: 0;
 }
 
 #user-image-grid {
   -webkit-user-drag: none;
   -webkit-user-select: none;
   display: inline-block;
   height: 264px;
   margin: 0;
   outline: none;
   overflow: hidden;
@@ skipping 196 matching lines @@
   padding: 2px;
   width: 220px;
 }
 
 #user-image-attribution {
   /* Turned off for now. */
   display: none;
 }
 
 #user-image .step-contents {
-  -webkit-margin-after: 30px;
   -webkit-margin-start: 31px;
+  margin-bottom: 30px;
 }
 
 .user-image-stream-area .spinner {
   display: none;
   height: 44px;
   left: 50%;
   margin-left: -22px;
   margin-top: -22px;
   position: absolute;
   top: 50%;
   width: 44px;
 }
 
 .camera.live:not(.online) .user-image-stream-area .spinner {
   display: block;
 }
 
 #user-images-loading {
   color: #9c9c9c;
 }