[Mac, Win] Show a user manager tutorial once per profile.

chrome/browser/resources/user_manager/user_manager_tutorial.js

 // Copyright 2014 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.
 
 cr.define('cr.ui.login', function() {
   /**
    * Constructs a slide manager for the user manager tutorial.
    *
    * @constructor
    */
@@ skipping 61 matching lines @@
     handleAddUserClick_: function(e) {
       chrome.send('addUser');
       $('user-manager-tutorial').hidden = true;
       // Prevent further propagation of click event. Otherwise, the click event
       // handler of document object will set wallpaper to user's wallpaper when
       // there is only one existing user. See http://crbug.com/166477
       e.stopPropagation();
     },
 
     endTutorial_: function(e) {
-      $('inner-container').style.opacity = '1';
-      $('inner-container').style.pointerEvents = '';
+      $('inner-container').classList.remove('disabled');
     },
 
     decorate: function() {
       // Transitions between the tutorial slides.
       for (var i = 0; i < this.slides_.length; ++i) {
         var buttonNext = $(this.slides_[i] + '-next');
         var buttonSkip = $(this.slides_[i] + '-skip');
         if (buttonNext)
           buttonNext.addEventListener('click', this.next_.bind(this));
         if (buttonSkip)
           buttonSkip.addEventListener('click', this.skip_.bind(this));
       }
       $('slide-add-user').addEventListener('click',
           this.handleAddUserClick_.bind(this));
     }
   };
 
   /**
    * Initializes the tutorial manager.
    */
   UserManagerTutorial.startTutorial = function() {
     $('user-manager-tutorial').hidden = false;
 
-    // Disable interacting with the pods while the tutorial is showing.
-    $('pod-row').focusPod();  // No focused pods.
-    $('inner-container').style.opacity = '0.4';
-    $('inner-container').style.pointerEvents = 'none';
+    // If there's only one pod, show the slides to the side of the pod.
+    // Otherwise, center the slides and disable interacting with the pods
+    // while the tutorial is showing.
+    if ($('pod-row').pods.length == 1) {
+      $('slide-welcome').classList.add('single-pod');
+      $('slide-your-chrome').classList.add('single-pod');
+      $('slide-complete').classList.add('single-pod');
+    } else {
+      $('pod-row').focusPod();  // No focused pods.
+      $('inner-container').classList.add('disabled');
+    }
   };
 
   /**
    * Initializes the tutorial manager.
    */
   UserManagerTutorial.initialize = function() {
     UserManagerTutorial.getInstance().decorate();
   };
 
   // Export.
   return {
     UserManagerTutorial: UserManagerTutorial
   };
 });