Take notification API out of experimental.

chrome/test/data/extensions/api_test/notifications/api/events/background.js

 // Copyright (c) 2012 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.
 
-const notification = chrome.experimental.notification;
+const notifications = chrome.notifications;
 
 var idString = "foo";
 
 var testBasicEvents = function() {
   var incidents = 0;
 
   var onCreateCallback = function(id) {
     chrome.test.assertTrue(id.length > 0);
     chrome.test.assertEq(idString, id);
     incidents++;
   }
 
   var onDisplayed = function(id) {
     incidents++;
     if (incidents == 2) {
       chrome.test.assertEq(idString, id);
       chrome.test.succeed();
     }
   }
-  notification.onDisplayed.addListener(onDisplayed);
+  notifications.onDisplayed.addListener(onDisplayed);
 
   var options = {
     templateType: "basic",
     iconUrl: "/icon.png",
     title: "Attention!",
     message: "Check out Cirque du Soleil"
   };
-  notification.create(idString, options, onCreateCallback);
+  notifications.create(idString, options, onCreateCallback);
+
 };
 
+
 chrome.test.runTests([ testBasicEvents ]);