Detect if webkitNotifications is available and remove webkit prefix (replaced

tests/html/exceptions_test.dart

 library ExceptionsTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 main() {
   useHtmlConfiguration();
-  test('DomException', () {
-    try {
-      window.webkitNotifications.createNotification('', '', '');
-    } on DomException catch (e) {
-      expect(e.code, DomException.SECURITY_ERR);
-      expect(e.name, 'SecurityError');
-      expect(e.message, 'SecurityError: DOM Exception 18');
-    }
-  });
+
   test('EventException', () {
     final event = new Event('Event');
     // Intentionally do not initialize it!
     try {
       document.$dom_dispatchEvent(event);
     } on EventException catch (e) {
       expect(e.code, EventException.UNSPECIFIED_EVENT_TYPE_ERR);
       expect(e.name, 'UNSPECIFIED_EVENT_TYPE_ERR');
-      expect(e.message, 'UNSPECIFIED_EVENT_TYPE_ERR: DOM Events Exception 0');
+      expect(e.message,
+          'UNSPECIFIED_EVENT_TYPE_ERR: DOM Events Exception 0');
     }
   });
 }