Back button for the WebView-based sign-in flow.

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 101 matching lines @@
         this.gaiaAuthHost_ = new cr.login.GaiaAuthHost(webview);
       } else {
         this.gaiaAuthHost_ = new cr.login.GaiaAuthHost($('signin-frame'));
       }
       this.gaiaAuthHost_.addEventListener(
           'ready', this.onAuthReady_.bind(this));
       this.gaiaAuthHost_.addEventListener(
           'dialogShown', this.onDialogShown_.bind(this));
       this.gaiaAuthHost_.addEventListener(
           'dialogHidden', this.onDialogHidden_.bind(this));
+      this.gaiaAuthHost_.addEventListener(
+          'backButton', this.onBackButton_.bind(this));
       this.gaiaAuthHost_.confirmPasswordCallback =
           this.onAuthConfirmPassword_.bind(this);
       this.gaiaAuthHost_.noPasswordCallback =
           this.onAuthNoPassword_.bind(this);
       this.gaiaAuthHost_.insecureContentBlockedCallback =
           this.onInsecureContentBlocked_.bind(this);
       this.gaiaAuthHost_.missingGaiaInfoCallback =
           this.missingGaiaInfo_.bind(this);
       this.gaiaAuthHost_.samlApiUsedCallback =
           this.samlApiUsed_.bind(this);
       this.gaiaAuthHost_.addEventListener('authFlowChange',
           this.onAuthFlowChange_.bind(this));
       this.gaiaAuthHost_.addEventListener('authCompleted',
           this.onAuthCompletedMessage_.bind(this));
 
       $('enterprise-info-hint-link').addEventListener('click', function(e) {
         chrome.send('launchHelpApp', [HELP_TOPIC_ENTERPRISE_REPORTING]);
         e.preventDefault();
       });
 
+      $('back-button-item').addEventListener('click', function(e) {
+        $('back-button-item').hidden = true;
+        $('signin-frame').back();
+        e.preventDefault();
+      }.bind(this));
       $('close-button-item').addEventListener('click', function(e) {
         this.cancel();
         e.preventDefault();
       }.bind(this));
 
       this.updateLocalizedContent();
     },
 
     /**
      * Header text of the screen.
@@ skipping 102 matching lines @@
       chrome.send('loginUIStateChanged', ['gaia-signin', true]);
       $('login-header-bar').signinUIState =
           this.isEnrollingConsumerManagement_ ?
               SIGNIN_UI_STATE.CONSUMER_MANAGEMENT_ENROLLMENT :
               SIGNIN_UI_STATE.GAIA_SIGNIN;
 
       // Ensure that GAIA signin (or loading UI) is actually visible.
       window.requestAnimationFrame(function() {
         chrome.send('loginVisible', ['gaia-loading']);
       });
+      $('back-button-item').disabled = false;
+      $('back-button-item').hidden = true;
       $('close-button-item').disabled = false;
       this.classList.toggle('loading', this.loading);
 
       // Button header is always visible when sign in is presented.
       // Header is hidden once GAIA reports on successful sign in.
       Oobe.getInstance().headerHidden = false;
     },
 
     onAfterShow: function(data) {
       if (!this.loading && this.isWebviewSignin)
@@ skipping 184 matching lines @@
 
       // Warm up the user images screen.
       Oobe.getInstance().preloadScreen({id: SCREEN_USER_IMAGE_PICKER});
     },
 
     /**
      * Invoked when the auth host emits 'dialogShown' event.
      * @private
      */
     onDialogShown_: function() {
+      $('back-button-item').disabled = true;
       $('close-button-item').disabled = true;
     },
 
     /**
      * Invoked when the auth host emits 'dialogHidden' event.
      * @private
      */
     onDialogHidden_: function() {
+      $('back-button-item').disabled = false;
       $('close-button-item').disabled = false;
     },
 
     /**
+     * Invoked when the auth host emits 'backButton' event.
+     * @private
+     */
+    onBackButton_: function(e) {
+      $('back-button-item').hidden = !e.detail;
+    },
+
+    /**
      * Invoked when the user has successfully authenticated via SAML, the
      * principals API was not used and the auth host needs the user to confirm
      * the scraped password.
      * @param {number} passwordCount The number of passwords that were scraped.
      * @private
      */
     onAuthConfirmPassword_: function(passwordCount) {
       this.loading = true;
       Oobe.getInstance().headerHidden = false;
 
@@ skipping 234 matching lines @@
      * For more info see C++ class 'WebUILoginView' which calls this method.
      * @param {number} error Error code.
      * @param {string} url The URL that failed to load.
      */
     onFrameError: function(error, url) {
       this.error_ = error;
       chrome.send('frameLoadingCompleted', [this.error_]);
     },
   };
 });