Show a spinner UI for zero-touch enrollment

chrome/browser/resources/chromeos/login/oobe_screen_oauth_enrollment.html

 <!-- Copyright 2015 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. -->
 
 <div id="oauth-enrollment" class="step no-logo hidden" hidden>
   <div id="oauth-enroll-step-contents">
     <div id="oauth-enroll-step-signin">
       <webview id="oauth-enroll-auth-view" name="oauth-enroll-auth-view">
       </webview>
     </div>
+    <div id="oauth-enroll-step-working">
+      <throbber-notice id="oauth-enroll-working-card"

[xiyuan, 2016/09/16 19:45:15]

Get rid of attribute "id" since it is not use. If it is used, we need a better
name, e.g. oauth-enroll-working-spiner, since this is not a card.

[kumarniranjan, 2016/09/16 20:53:40]

Done.

+          i18n-values="text:oauthEnrollWorking">
+      </throbber-notice>
+    </div>
     <div id="oauth-enroll-step-error" role="alert">
       <notification-card id="oauth-enroll-error-card" type="fail"
           i18n-values="button-label:oauthEnrollRetry">
       </notification-card>
     </div>
     <div id="oauth-enroll-step-success" role="alert">
       <notification-card id="oauth-enroll-success-card" type="success"
           i18n-values="button-label:oauthEnrollDone"
           i18n-content="oauthEnrollSuccess">
       </notification-card>
@@ skipping 38 matching lines @@
       <notification-card id="oauth-enroll-attribute-prompt-error-card"
           type="fail" i18n-values="button-label:oauthEnrollDone">
       </notification-card>
     </div>
   </div>
   <div id="oauth-saml-notice-container">
     <span id="oauth-saml-notice-message"></span>
   </div>
   <navigation-bar id="oauth-enroll-navigation"></navigation-bar>
 </div>