Enable wallpaper boot animation for boot into sign in too. Add flag to disable it.

chrome/browser/resources/chromeos/login/user_pod_row.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 User pod row implementation.
  */
 
 cr.define('login', function() {
   /**
@@ skipping 15 matching lines @@
    * @type {number}
    * @const
    */
   var WALLPAPER_LOAD_DELAY_MS = 500;
 
   /**
    * Wallpaper load delay in milliseconds. TODO(nkostylev): Tune this constant.
    * @type {number}
    * @const
    */
-  var WALLPAPER_BOAT_LOAD_DELAY_MS = 500;
+  var WALLPAPER_BOOT_LOAD_DELAY_MS = 500;
 
   /**
    * Oauth token status. These must match UserManager::OAuthTokenStatus.
    * @enum {number}
    * @const
    */
   var OAuthTokenStatus = {
     UNKNOWN: 0,
     INVALID: 1,
     VALID: 2
@@ skipping 625 matching lines @@
               this.loadWallpaper_.bind(this), WALLPAPER_LOAD_DELAY_MS);
         } else {
           if (!this.firstShown_) {
             // Load wallpaper immediately if there no pod was focused
             // previously, and it is not a boot into user pod list case.
             this.loadWallpaper_();
           } else {
             // Boot transition. Delay wallpaper load to remove jank
             // happening when wallpaper load is competing for resources with
             // login WebUI.
-            this.loadWallpaperTimeout_ = window.setTimeout(
-                this.loadWallpaper_.bind(this), WALLPAPER_BOAT_LOAD_DELAY_MS);
+            if (Oobe.getInstance().shouldLoadWallpaperOnBoot()) {
+              this.loadWallpaperTimeout_ = window.setTimeout(
+                  this.loadWallpaper_.bind(this), WALLPAPER_BOOT_LOAD_DELAY_MS);
+            }
             this.firstShown_ = false;
           }
         }
       } else {
         chrome.send('userDeselected');
       }
       this.insideFocusPod_ = false;
     },
 
     loadWallpaper_: function() {
@@ skipping 225 matching lines @@
           chrome.send('loginVisible');
         });
       }
     }
   };
 
   return {
     PodRow: PodRow
   };
 });