DOMUI prefs: Add and wire up a stub overlay for adding a startup page.

chrome/browser/resources/options/add_startup_page_overlay.js

+// Copyright (c) 2010 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.
+
+/**
+ * AddStartupPageOverlay class
+ * Encapsulated handling of the 'Add Page' overlay page.
+ * @class
+ */
+function AddStartupPageOverlay() {
+  OptionsPage.call(this, 'addStartupPageOverlay',
+                   templateData.addStartupPageTitle,
+                   'addStartupPageOverlay');
+}
+
+cr.addSingletonGetter(AddStartupPageOverlay);
+
+AddStartupPageOverlay.prototype = {
+  __proto__: OptionsPage.prototype,
+
+  /**
+   * Initializes the page.
+   */
+  initializePage: function() {
+    OptionsPage.prototype.initializePage.call(this);
+
+    $('addStartupPageCancelButton').onclick = function(e) {
+      OptionsPage.clearOverlays();
+    };
+  }
+};