[cros,login] Pre-load login extension in the background.

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

 // Copyright (c) 2011 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 Account picker screen implementation.
  */
 
 cr.define('login', function() {
   /**
@@ skipping 24 matching lines @@
     firstShown_ : true,
 
     /**
      * Event handler that is invoked just before the frame is shown.
      * @param data {string} Screen init payload.
      */
     onBeforeShow: function(data) {
       $('pod-row').handleShow();
       if (this.firstShown_) {
         this.firstShown_ = false;
-        $('pod-row').startInitAnimation();
+        // TODO(nkostylev): Enable animation back when session start jank
+        // is reduced. See http://crosbug.com/11116 http://crosbug.com/18307
+        // $('pod-row').startInitAnimation();
+
+        // TODO(altimofeev): Call it after animation has stoped when animation
+        // is enabled.
+        chrome.send('accountPickerReady', []);
       }
     },
 
      /**
       * Event handler that is invoked just before the frame is hidden.
       * @param data {string} Screen init payload.
       */
     onBeforeHide: function(data) {
       $('pod-row').handleHide();
     }
@@ skipping 15 matching lines @@
    * @public
    */
   AccountPickerScreen.setCapsLockState = function(enabled) {
     $('pod-row').classList[enabled ? 'add' : 'remove']('capslock-on');
   };
 
   return {
     AccountPickerScreen: AccountPickerScreen
   };
 });