First try at a user management screen for the desktop

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

Index: chrome/browser/resources/chromeos/login/display_manager.js
diff --git a/chrome/browser/resources/chromeos/login/display_manager.js b/chrome/browser/resources/chromeos/login/display_manager.js
index 9988cb42e6e7ed92daf8e54e5434dc681531a72e..40448a69d4990afcffb5295a33c5a3fff56ba090 100644
--- a/chrome/browser/resources/chromeos/login/display_manager.js
+++ b/chrome/browser/resources/chromeos/login/display_manager.js
@@ -417,7 +417,9 @@ cr.define('cr.ui.login', function() {
       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);
     },