dart2js: run dartfmt on tests

tests/compiler/dart2js_extra/23404_test.dart

 // Copyright (c) 2015, 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.
 
 // Regression test for http://dartbug.com/23404/
 import 'package:expect/expect.dart';
 
 // Dart2js crashed when the global metadata had escaped characters. That
 // happens, for example, when tearing off a function that uses a default
 // argument containing escape characters.
-foo([a='\u00a0']) => a;
+foo([a = '\u00a0']) => a;
 bar() => '';
 
 @NoInline()
 @AssumeDynamic()
 confuse(x) => x;
 
 main() {
   Expect.equals('\u00a0', confuse(foo)());
   Expect.equals('', confuse(bar)());
 }