dart2js: run dartfmt on tests

tests/compiler/dart2js_extra/21351_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.
 
 class A {
   bool _flag = false;
   bool get flag => _flag;
 }
 
-main () {
-  var value1, value2; 
+main() {
+  var value1, value2;
   var count = 0;
 
   for (var x = 0; x < 10; x++) {
     var otherThing = new A();
     for (var dummy = 0; dummy < x; dummy++) {
       otherThing._flag = !otherThing._flag;
     }
 
     value1 = value2;
     value2 = otherThing;
 
     if (value1 == null) continue;
 
     if (value1.flag) count++;
   }
 
   if (count == 0) throw "FAIL";
 }
-