Always show login header bar on the account picker screen.

ui/login/account_picker/screen_account_picker.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.
 
 /**
  * @fileoverview Account picker screen implementation.
  */
 
 login.createScreen('AccountPickerScreen', 'account-picker', function() {
   /**
@@ skipping 100 matching lines @@
     },
 
     /**
      * Event handler that is invoked just before the frame is shown.
      * @param {string} data Screen init payload.
      */
     onBeforeShow: function(data) {
       this.showing_ = true;
       chrome.send('loginUIStateChanged', ['account-picker', true]);
       $('login-header-bar').signinUIState = SIGNIN_UI_STATE.ACCOUNT_PICKER;
+      // Header bar should be always visible on Account Picker screen.
+      Oobe.getInstance().headerHidden = false;
       chrome.send('hideCaptivePortal');
       var podRow = $('pod-row');
       podRow.handleBeforeShow();
 
       // In case of the preselected pod onShow will be called once pod
       // receives focus.
       if (!podRow.preselectedPod)
         this.onShow();
     },
 
@@ skipping 344 matching lines @@
      * @param {string} userID The user ID of the public session
      * @param {string} locale The locale to which this list of keyboard layouts
      *     applies
      * @param {!Object} list List of available keyboard layouts
      */
     setPublicSessionKeyboardLayouts: function(userID, locale, list) {
       $('pod-row').setPublicSessionKeyboardLayouts(userID, locale, list);
     }
   };
 });