Fixing tests after event constructor change.

tests/html/storage_test.dart

 library StorageTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 
 main() {
   useHtmlConfiguration();
   test('GetItem', () {
     final value = window.localStorage['does not exist'];
     expect(value, isNull);
   });
   test('SetItem', () {
     final key = 'foo';
     final value = 'bar';
     window.localStorage[key] = value;
     final stored = window.localStorage[key];
     expect(stored, value);
   });
 
   test('event', () {
-    var event = new StorageEvent('something', oldValue: 'old', newValue: 'new');
+    // Bug 8076 that not all optional params are optional in Dartium.
+    var event = new StorageEvent('something', oldValue: 'old', newValue: 'new',
+        url: 'url');
     expect(event is StorageEvent, isTrue);
     expect(event.oldValue, 'old');
     expect(event.newValue, 'new');
   });
 }