dart2js: run dartfmt on tests

tests/compiler/dart2js/null_check_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.
 
 import "package:expect/expect.dart";
 import 'compiler_helper.dart';
 import "package:async_helper/async_helper.dart";
 
 const String TEST1 = r"""
 main() {
   var foo;
   if (main() == 5) {
     foo = [0];
   }
   return foo[0];
 }
 """;
 
 main() {
   asyncTest(() => compileAll(TEST1).then((generated) {
-    Expect.isFalse(generated.contains('foo.length'));
-  }));
+        Expect.isFalse(generated.contains('foo.length'));
+      }));
 }