First try at a user management screen for the desktop

chrome/browser/resources/chromeos/login/display_manager.js

 // 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.
 
 /**
  * @fileoverview Display manager for WebUI OOBE and login.
  */
 
 // TODO(xiyuan): Find a better to share those constants.
 /** @const */ var SCREEN_OOBE_NETWORK = 'connect';
@@ skipping 399 matching lines @@
 
       var header = document.createElement('span');
       header.id = 'header-' + screenId;
       header.textContent = el.header ? el.header : '';
       header.className = 'header-section';
       $('header-sections').appendChild(header);
 
       var dot = document.createElement('div');
       dot.id = screenId + '-dot';
       dot.className = 'progdot';
-      $('progress-dots').appendChild(dot);
+      var progressDots = $('progress-dots');
+      if (progressDots)
+        progressDots.appendChild(dot);
 
       this.appendButtons_(el.buttons, screenId);
     },
 
     /**
      * Updates inner container size based on the size of the current screen and
      * other screens in the same group.
      * Should be executed on screen change / screen size change.
      * @param {!HTMLElement} screen Screen that is being shown.
      */
@@ skipping 291 matching lines @@
    */
   DisplayManager.refocusCurrentPod = function() {
     $('pod-row').refocusCurrentPod();
   };
 
   // Export
   return {
     DisplayManager: DisplayManager
   };
 });