Show guest button based on extension parameter guestSignin.

chrome/browser/resources/chromeos/login/screen_gaia_signin.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 Oobe signin screen implementation.
  */
 
 login.createScreen('GaiaSigninScreen', 'gaia-signin', function() {
   // Gaia loading time after which error message must be displayed and
@@ skipping 405 matching lines @@
       }
 
       if (data.localizedStrings)
         params.localizedStrings = data.localizedStrings;
 
       if (this.isNewGaiaFlow) {
         $('inner-container').classList.add('new-gaia-flow');
         $('progress-dots').hidden = true;
         params.chromeType = data.chromeType;
         params.isNewGaiaFlowChromeOS = true;
-        $('login-header-bar').showGuestButton = true;
       }
 
       if (data.gaiaEndpoint)
         params.gaiaPath = data.gaiaEndpoint;
 
       $('login-header-bar').newGaiaFlow = this.isNewGaiaFlow;
 
       // Screen size could have been changed because of 'new-gaia-flow' or
       // 'full-width' classes.
       if (Oobe.getInstance().currentScreen === this)
@@ skipping 36 matching lines @@
         reasonLabel.textContent =
             loadTimeData.getString('signinScreenPasswordChanged');
         reasonLabel.hidden = false;
       } else {
         reasonLabel.hidden = true;
       }
 
       if (this.isNewGaiaFlow) {
         $('login-header-bar').showCreateSupervisedButton =
             data.supervisedUsersCanCreate;
+        $('login-header-bar').showGuestButton = data.guestSignin;
       } else {
         $('createAccount').hidden = !data.createAccount;
         $('guestSignin').hidden = !data.guestSignin;
         $('createSupervisedUserPane').hidden = !data.supervisedUsersEnabled;
 
         $('createSupervisedUserLinkPlaceholder').hidden =
             !data.supervisedUsersCanCreate;
         $('createSupervisedUserNoManagerText').hidden =
             data.supervisedUsersCanCreate;
         $('createSupervisedUserNoManagerText').textContent =
@@ skipping 474 matching lines @@
      */
     updateDeviceId: function(data) {
       if (!this.isNewGaiaFlow)
         return;
 
       if (data && data.deviceId)
         this.gaiaAuthHost_.updateDeviceId(data.deviceId);
     },
   };
 });