[ChromeOS] Reland - Make WebUI login use only needed resources.

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

+// Copyright (c) 2011 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 Login UI header bar implementation.
+ */
+
+cr.define('login', function() {
+
+  /**
+   * Creates a header bar element.
+   * @constructor
+   * @extends {HTMLDivElement}
+   */
+  var HeaderBar = cr.ui.define('div');
+
+  HeaderBar.prototype = {
+    __proto__: HTMLDivElement.prototype,
+
+    /** @inheritDoc */
+    decorate: function() {
+      $('shutdown-button').addEventListener('click', function(e) {
+        chrome.send('shutdownSystem');
+      });
+      $('add-user-button').addEventListener('click', function(e) {
+        if (window.navigator.onLine) {
+          Oobe.showSigninUI();
+        } else {
+          $('bubble').showTextForElement($('add-user-button'),
+              localStrings.getString('addUserOfflineMessage'));
+        }
+      });
+      $('cancel-add-user-button').addEventListener('click', function(e) {
+        this.hidden = true;
+        $('add-user-button').hidden = false;
+        Oobe.showScreen({id: SCREEN_ACCOUNT_PICKER});
+      });
+    }
+  };
+
+  return {
+    HeaderBar: HeaderBar
+  };
+});