Fix type tests for null.

tests/language/null_is2_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
-// Test that dart2js treats [:this():] as a closure send.
-
 import "package:expect/expect.dart";
 
-class A {
-  call() => 42;
-  test1() => this();
-  test2() => (this)();
+class Test<T> {
+  foo(a) => a is T;
 }
 
 main() {
-  Expect.equals(42, (new A()).test1());
-  Expect.equals(42, (new A()).test2());
+  Expect.isTrue(new Test<Object>().foo(null));
+  Expect.isTrue(new Test<dynamic>().foo(null));
+  Expect.isFalse(new Test<int>().foo(null));
+  Expect.isFalse(null is List<Object>);
 }