dart2js: run dartfmt on tests

tests/compiler/dart2js_extra/regress/4515_3_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";
 
 class A {
   a(x) => x + 1;
 }
 
 f(p) => p("A");
 
 main() {
   A a = new A();
   a.a(1);
   var v = null;
   try {
     v = f(a.a);
-  } catch (e) { }
+  } catch (e) {}
 
   Expect.equals(null, v);
 }