Minimal attestation-based enrollment flow.

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

 // 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.
 
 login.createScreen('OAuthEnrollmentScreen', 'oauth-enrollment', function() {
   /* Code which is embedded inside of the webview. See below for details.
   /** @const */ var INJECTED_WEBVIEW_SCRIPT = String.raw`
                       (function() {
                          <include src="../keyboard/keyboard_utils.js">
                          keyboard.initializeKeyboardFlow();
@@ skipping 213 matching lines @@
      * Shows attribute-prompt step with pre-filled asset ID and
      * location.
      */
     showAttributePromptStep: function(annotated_asset_id, annotated_location) {
       $('oauth-enroll-asset-id').value = annotated_asset_id;
       $('oauth-enroll-location').value = annotated_location;
       this.showStep(STEP_ATTRIBUTE_PROMPT);
     },
 
     /**
-     * Cancels enrollment and drops the user back to the login screen.
+     * Cancels the current authentication and drops the user back to the next
+     * screen (either the next authentication or the login screen).
      */
     cancel: function() {
       if (this.isCancelDisabled)
         return;
       this.isCancelDisabled = true;
       chrome.send('oauthEnrollClose', ['cancel']);
     },
 
     /**
      * Switches between the different steps in the enrollment flow.
@@ skipping 25 matching lines @@
      * Sets an error message and switches to the error screen.
      * @param {string} message the error message.
      * @param {boolean} retry whether the retry link should be shown.
      */
     showError: function(message, retry) {
       if (this.currentStep_ == STEP_ATTRIBUTE_PROMPT) {
         $('oauth-enroll-attribute-prompt-error-card').textContent = message;
         this.showStep(STEP_ATTRIBUTE_PROMPT_ERROR);
         return;
       }
+      this.isCancelDisabled_ = false;
       $('oauth-enroll-error-card').textContent = message;
       $('oauth-enroll-error-card').buttonLabel =
           retry ? loadTimeData.getString('oauthEnrollRetry') : '';
       this.showStep(STEP_ERROR);
     },
 
     doReload: function() {
       this.lastBackMessageValue_ = false;
       this.authenticator_.reload();
       this.updateControlsState();
@@ skipping 44 matching lines @@
                                      this.lastBackMessageValue_;
       this.navigation_.refreshVisible = this.isAtTheBeginning() &&
                                         !this.isManualEnrollment_;
       this.navigation_.closeVisible = (this.currentStep_ == STEP_SIGNIN ||
                                        this.currentStep_ == STEP_ERROR) &&
                                       !this.navigation_.refreshVisible;
       $('login-header-bar').updateUI_();
     }
   };
 });