dart2js: run dartfmt on tests

tests/compiler/dart2js_extra/deferred/deferred_mirrors2_lib3.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.
 
 library lib3;
 
 import 'deferred_mirrors2_lib4.dart';
 
-@MirrorsUsed(targets: const [
-    'lib3'
-])
+@MirrorsUsed(targets: const ['lib3'])
 import 'dart:mirrors';
 
 class R {
   void bind(Type type) {
     ClassMirror classMirror = _reflectClass(type);
     MethodMirror ctor = classMirror.declarations[classMirror.simpleName];
     int length = ctor.parameters.length;
     Function create = classMirror.newInstance;
   }
 }