Use PageManager in About page

chrome/browser/resources/uber/uber_page_manager_observer.js

+// Copyright 2014 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.
+
+cr.define('uber', function() {
+  var PageManager = cr.ui.pageManager.PageManager;
+
+  /**
+   * A PageManager observer that updates the uber page.
+   * @constructor
+   * @implements {PageManager.Observer}
+   */
+  function PageManagerObserver() {}
+
+  PageManagerObserver.prototype = {
+    __proto__: PageManager.Observer.prototype,
+
+    /**
+     * Informs the uber page when a top-level overlay is opened or closed.
+     * @param {Page} page The page that is being shown or was hidden.
+     * @override
+     */
+    onPageVisibilityChanged: function(page) {
+      if (PageManager.isTopLevelOverlay(page)) {
+        if (page.visible)
+          uber.invokeMethodOnParent('beginInterceptingEvents');
+        else
+          uber.invokeMethodOnParent('stopInterceptingEvents');
+      }
+    },
+
+    /**
+     * Uses uber to set the title.
+     * @param {string} title The title to set.
+     * @override
+     */
+    updateTitle: function(title) {
+      uber.setTitle(title);
+    },
+
+    /**
+     * Pushes the current page onto the history stack, replacing the current
+     * entry if appropriate.
+     * @param {string} path The path of the page to push onto the stack.
+     * @param {boolean} replace If true, allow no history events to be created.
+     * @override
+     */
+    updateHistory: function(path, replace) {
+      var historyFunction = replace ? uber.replaceState : uber.pushState;
+      historyFunction({}, path);
+    },
+  };
+
+  // Export
+  return {
+    PageManagerObserver: PageManagerObserver
+  };
+});