dart2js: run dartfmt on tests

tests/compiler/dart2js_extra/mirrors_used_warning2_test.dart

 // Copyright (c) 2014, 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 'dart:mirrors';
 import 'dart:async';
 
 import 'package:expect/expect.dart';
 
 class A {
@@ skipping 12 matching lines @@
   // Dart2js should retain all symbols.
   Expect.equals("foo", new A().foo);
   Expect.isTrue(lines.isEmpty);
   var barResult = new A().bar;
   Expect.equals("bar", barResult);
   Expect.isTrue(lines.isEmpty);
 }
 
 main() {
   runZoned(runTests,
-           zoneSpecification: new ZoneSpecification(print: capturePrint));
+      zoneSpecification: new ZoneSpecification(print: capturePrint));
 }