Add error handling for supervised user import flow.

chrome/browser/resources/options/managed_user_import.js

Index: chrome/browser/resources/options/managed_user_import.js
diff --git a/chrome/browser/resources/options/managed_user_import.js b/chrome/browser/resources/options/managed_user_import.js
index 70a54dd2cabfc54e54649f882a613e911981fca3..9f36a77ed081f920c51455d8286eee255fe5ce7b 100644
--- a/chrome/browser/resources/options/managed_user_import.js
+++ b/chrome/browser/resources/options/managed_user_import.js
@@ -7,6 +7,95 @@ cr.define('options', function() {
   var ArrayDataModel = cr.ui.ArrayDataModel;
 
   /**
+   * ManagedUserList class.
+   * Handles requests for retrieving a list of existing managed users which are
+   * supervised by the current profile. This list is cached in order to make it
+   * possible to serve future requests immediately. The first request will be
+   * handled asynchronously.
+   * @constructor
+   * @class
+   */
+  function ManagedUserList() {
+    this.callbacks_ = [];
+    this.errbacks_ = [];
+    this.requestInProgress_ = false;
+    this.managedUsers = null;
+  };
+
+  cr.addSingletonGetter(ManagedUserList);
+
+  /**
+   * Resets to the initial state of no pending requests.
+   * @private
+   */
+  ManagedUserList.prototype.reset_ = function() {
+    this.callbacks_ = [];
+    this.errbacks_ = [];
+    this.requestInProgress_ = false;
+  }
+
+  /**
+   * Receives a list of managed users and passes the list to each of the
+   * callbacks.
+   * @param {Array.<Object>} managedUsers An array of managed user objects.
+   *     Each object is of the form:
+   *       managedUser = {
+   *         id: "Managed User ID",
+   *         name: "Managed User Name",
+   *         iconURL: "chrome://path/to/icon/image",
+   *         onCurrentDevice: true or false,
+   *         needAvatar: true or false
+   *       }
+   */
+  ManagedUserList.receiveExistingManagedUsers = function(managedUsers) {
+    var instance = ManagedUserList.getInstance();
+    var i;
+    for (i = 0; i < instance.callbacks_.length; i++) {
+      instance.callbacks_[i](managedUsers);
+    }
+    this.managedUsers = managedUsers;
+    instance.reset_();
+  };
+
+  /**
+   * Called when there is a signin error when retrieving the list of managed
+   * users. Calls the error callbacks which will display an appropriate error
+   * message to the user.
+   */
+  ManagedUserList.onSigninError = function() {
+    var instance = ManagedUserList.getInstance();
+    var i;
+    for (i = 0; i < instance.errbacks_.length; i++) {
+      instance.errbacks_[i]();
+    }
+    // Reset the list of managed users in order to avoid showing stale data.
+    instance.managedUsers = null;
+    instance.reset_();
+  };
+
+  /**
+   * Handles the request for the list of existing managed users. If the data is
+   * already available, it will call |callback| immediately. Otherwise, it
+   * retrieves the list of existing managed users which is then processed in
+   * receiveExistingManagedUsers().
+   * @param {Object} callback The callback function which is called on success.
+   * @param {Object} errback the callback function which is called on error.
+   */
+  ManagedUserList.requestExistingManagedUsers = function(callback, errback) {
+    var instance = ManagedUserList.getInstance();
+    instance.callbacks_.push(callback);
+    instance.errbacks_.push(errback);
+    if (!instance.requestInProgress_) {
+      if (instance.managedUsers != null) {
+        ManagedUserList.receiveExistingManagedUsers(instance.managedUsers);
+        return;
+      }
+      instance.requestInProgress_ = true;
+      chrome.send('requestManagedUserImportUpdate');
+    }
+  };
+
+  /**
    * ManagedUserImportOverlay class.
    * Encapsulated handling of the 'Import existing managed user' overlay page.
    * @constructor
@@ -75,7 +164,8 @@ cr.define('options', function() {
      * @override
      */
     didShowPage: function() {
-      chrome.send('requestManagedUserImportUpdate');
+      ManagedUserList.requestExistingManagedUsers(
+          this.receiveExistingManagedUsers_, this.onSigninError_.bind(this));
 
       this.updateImportInProgress_(false);
       $('managed-user-import-error-bubble').hidden = true;
@@ -157,8 +247,7 @@ cr.define('options', function() {
     },
 
     /**
-     * Adds all the existing |managedUsers| to the list. If |managedUsers|
-     * is undefined, then the list is cleared.
+     * Sets the data model of the managed user list to |managedUsers|.
      * @param {Array.<Object>} managedUsers An array of managed user objects.
      *     Each object is of the form:
      *       managedUser = {
@@ -171,11 +260,6 @@ cr.define('options', function() {
      * @private
      */
     receiveExistingManagedUsers_: function(managedUsers) {
-      if (!managedUsers) {
-        $('managed-user-list').dataModel = null;
-        return;
-      }
-
       managedUsers.sort(function(a, b) {
         return a.name.localeCompare(b.name);
       });
@@ -184,14 +268,15 @@ cr.define('options', function() {
       if (managedUsers.length == 0) {
         this.onError_(loadTimeData.getString('noExistingManagedUsers'));
         $('managed-user-import-ok').disabled = true;
+      } else {
+        // Hide the error bubble.
+        $('managed-user-import-error-bubble').hidden = true;
       }
     },
 
-    /**
-     * @private
-     */
-    hideErrorBubble_: function() {
-      $('managed-user-import-error-bubble').hidden = true;
+    onSigninError_: function() {
+      $('managed-user-list').dataModel = null;
+      this.onError_(loadTimeData.getString('managedUserImportSigninError'));
     },
 
     /**
@@ -220,10 +305,7 @@ cr.define('options', function() {
 
   // Forward public APIs to private implementations.
   [
-    'hideErrorBubble',
-    'onError',
     'onSuccess',
-    'receiveExistingManagedUsers',
   ].forEach(function(name) {
     ManagedUserImportOverlay[name] = function() {
       var instance = ManagedUserImportOverlay.getInstance();
@@ -234,5 +316,6 @@ cr.define('options', function() {
   // Export
   return {
     ManagedUserImportOverlay: ManagedUserImportOverlay,
+    ManagedUserList: ManagedUserList,
   };
 });