MD User Manager: Display error message when all profiles are locked.

chrome/browser/resources/md_user_manager/user_manager.js

 // Copyright 2016 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.
 
 <include src="../../../../ui/login/screen.js">
 <include src="../../../../ui/login/bubble.js">
 <include src="../../../../ui/login/login_ui_tools.js">
 <include src="../../../../ui/login/display_manager.js">
 <include src="../../../../ui/login/account_picker/user_pod_template.js">
 <include src="../../../../ui/login/account_picker/screen_account_picker.js">
@@ skipping 48 matching lines @@
   /**
    * Initializes the UserManager.
    */
   UserManager.initialize = function() {
     cr.ui.login.DisplayManager.initialize();
     login.AccountPickerScreen.register();
     cr.ui.Bubble.decorate($('bubble'));
 
     signin.ProfileBrowserProxyImpl.getInstance().initializeUserManager(
         window.location.hash);
+    cr.addWebUIListener('show-error-dialog', cr.ui.UserManager.showErrorDialog);

[dpapad, 2016/05/31 19:11:59]

Should this listener be removed at some point? Is there any way the 'initialize'
method is executed twice and we end up with two or more listeners?

Polymer code solves this issue by using WebUIListenerBehavior which
automatically removes listeners within the "detached" lifecyle method. See
example at
https://code.google.com/p/chromium/codesearch#chromium/src/chrome/browser/res....

[Moe, 2016/05/31 20:53:05]

user_manager.js is executed in the top level html and initialize() is called on
DOMContentLoaded which is expected to be called only once during the lifetime of
chrome://md-user-manager/. Since we expect the listener to be around as long as
the page lives can we not bother with detaching it at all?

similarly, if the component, once attached, is meant to stick around during the
lifetime of the page do we have to use WebUIListenerBehavior to detach the
listeners?

[dpapad, 2016/05/31 21:05:51]

If it is guaranteed that initialized() is called only once, then it is fine to
never remove the listener. Perhaps adding a very short comment can save future
readers some time.
// Listener is purposefully active for the lifetime of this page.


Regarding Polymer components, it is OK to never remove it if the component is
never detached, but it also does not hurt to always use the
WebUIListenerBehavior. It makes it more robust to future optimizations where a
component is removed from the DOM when not visible. For example in md_settings,
which is a fairly large page, several things are removed from the DOM when not
needed. This is especially true for listeners registered by dialogs.

   };
 
   /**
    * Shows the given screen.
    * @param {boolean} showGuest True if 'Browse as Guest' button should be
    *     displayed.
    * @param {boolean} showAddPerson True if 'Add Person' button should be
    *     displayed.
    */
   UserManager.showUserManagerScreen = function(showGuest, showAddPerson) {
@@ skipping 46 matching lines @@
     DisplayManager.showSignInError(loginAttempts, message, link, helpId);
   };
 
   /**
    * Clears error bubble as well as optional menus that could be open.
    */
   UserManager.clearErrors = function() {
     DisplayManager.clearErrors();
   };
 
+  /**
+   * Shows the error dialog populated with the given message.
+   * @param {string} message Error message to show.
+   */
+  UserManager.showErrorDialog = function(message) {
+    document.querySelector('error-dialog').show(message);
+  };
+
   // Export
   return {
     UserManager: UserManager
   };
 });
 
 // Alias to Oobe for use in src/ui/login/account_picker/user_pod_row.js
 var Oobe = cr.ui.UserManager;
 
 // Allow selection events on components with editable text (password field)
 // bug (http://code.google.com/p/chromium/issues/detail?id=125863)
 disableTextSelectAndDrag(function(e) {
   var src = e.target;
   return src instanceof HTMLTextAreaElement ||
          src instanceof HTMLInputElement &&
          /text|password|search/.test(src.type);
 });
 
 document.addEventListener('DOMContentLoaded', cr.ui.UserManager.initialize);