Fixing conversion of null event targets.

tests/html/mouse_event_test.dart

Index: tests/html/mouse_event_test.dart
diff --git a/tests/html/non_instantiated_is_test.dart b/tests/html/mouse_event_test.dart
similarity index 65%
copy from tests/html/non_instantiated_is_test.dart
copy to tests/html/mouse_event_test.dart
index bf1ece1419bbfc49c5f4efa06ae8fe440ca85fba..4be967bda1b0d60fb55b220d9231f8480fa70328 100644
--- a/tests/html/non_instantiated_is_test.dart
+++ b/tests/html/mouse_event_test.dart
@@ -2,19 +2,16 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// Regression test for dart2js, that used to emit wrong code on is
-// checks of native classes that are not instantiated.
-
-import 'dart:html';
+library mouse_event_test;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
-
-var a = [new Object()];
+import 'dart:html';
 
 main() {
   useHtmlConfiguration();
 
-  test('is', () {
-    expect(a[0] is Node, isFalse);
+  test('relatedTarget', () {
+    var event = new MouseEvent('mouseout');
+    expect(event.relatedTarget, isNull);
   });
 }