updated UI, default profile name, check for existing supervised user before create

chrome/browser/resources/md_user_manager/control_bar.css

 /* Copyright 2016 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. */
 
-#login-header-bar {
-  bottom: 0;
-  left: 0;
-  min-height: 32px;
+#container {
   padding-bottom: 12px;
   padding-top: 12px;
-  position: absolute;
-  right: 0;
 }
 
 paper-button {
   border-radius: 2px;
+  color: var(--paper-grey-600);
+  font-weight: 500;
   line-height: 32px;
+  margin: 0;
   min-width: 52px;
   padding: 0 16px;
 }
 
 #addUser {
-  -webkit-margin-end: 16px;
+  margin: 0 8px;
 }
 
 #logo {
   content: -webkit-image-set(
       url(../../../app/theme/default_100_percent/%DISTRIBUTION%/product_logo_name_48.png) 1x,
       url(../../../app/theme/default_200_percent/%DISTRIBUTION%/product_logo_name_48.png) 2x);
   height: 18px;
   left: 24px;
   position: absolute;
   top: 19px;
 }
 
 :host-context([dir='rtl']) #logo {
   left: auto;
   right: 24px;
 }