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

chrome/browser/resources/md_user_manager/user_manager.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. */
 
 body {
   background-color: #eee;
 }
 
+#login-header-bar {
+  bottom: 0;
+  left: 0;
+  position: absolute;
+  right: 0;
+}
+
 /* Overrides for the desktop user manager screen. */
 
 #outer-container {
   min-height: 0;
 }
 
 .bubble.faded {
   opacity: 0;
 }
 
@@ skipping 179 matching lines @@
 .action-box-remove-user-warning .remove-warning-button {
   height: 30px;
 }
 
 .action-box-remove-user-warning .remove-warning-button:focus {
   /* Override the default blue border inherited from
   button.custom-appearance:focus. */
   border: 1px solid transparent !important;
   box-shadow: inset 0 0 0 1px #fff;
 }