Extract common HTML from oobe.html/login.html.

chrome/browser/resources/chromeos/login/oobe.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.
  *
  * This is the stylesheet used by the Out of the box experience (OOBE) flow,
  * sign in and lock screens.
  */
 
 html,
 body {
@@ skipping 99 matching lines @@
 
 #oobe.error-message #inner-container,
 #oobe.tpm-error-message #inner-container {
   box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.3),
               0 4px 23px 5px rgba(0, 0, 0, 0.2),
               0 2px 6px rgba(0, 0, 0, 0.15);
 
 }
 
 /* Only play this animation when 'down' class is removed. */
-#inner-container:not(.down) {
+.oobe-display #inner-container:not(.down) {
   -webkit-transition: -webkit-transform 200ms ease-in-out;
 }
 
-#inner-container.down {
+.oobe-display #inner-container.down {
   -webkit-transform: translateY(50px) rotateX(-2.5deg);
 }
 
 #eula #stats-help-link {
   color: rgb(49, 106, 197);
 }
 
 #step-logo {
   -webkit-margin-start: 17px;
   display: -webkit-box;
@@ skipping 89 matching lines @@
   -webkit-transform: translateX(-50px)
 }
 
 #progress-dots {
   -webkit-box-pack: center;
   -webkit-margin-before: 15px;
   display: -webkit-box;
 }
 
 /* Hidden for the duration of initial transition. */
-#progress-dots.down {
+.oobe-display #progress-dots.down {
   visibility: hidden;
 }
 
 .progdot {
   -webkit-margin-end: 12px;
   background: white;
   height: 10px;
   opacity: 0.4;
   width: 10px;
 }
@@ skipping 875 matching lines @@
 }
 
 .background-initial {
   opacity: 0;
 }
 
 .background-final {
   opacity: 1;
 }