dart2js: run dartfmt on tests

tests/compiler/dart2js_native/js_constant_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.
 
 import 'dart:_foreign_helper' show JS;
 import "package:expect/expect.dart";
 
 // Negative constant numbers must be generated as negation, not just a literal
 // with a sign, i.e.
 //
 //     (-5).toString()
 //
 // not
 //
 //     -5 .toString()
 //
 // The unparethesized version is `-(5 .toString())`, which creates the string
 // `"5"`, then converts it to a number for negation, giving a number result
 // instead of a string result.
 
 @NoInline()
 checkString(r) {
-  Expect.isTrue(r is String,
-      'Expected string, found ${r} of type ${r.runtimeType}');
+  Expect.isTrue(
+      r is String, 'Expected string, found ${r} of type ${r.runtimeType}');
 }
 
 test1() {
   checkString(JS('', '#.toString()', -5));
 }
 
 test2() {
   checkString(JS('', '#.toString()', -1.5));
 }
 
 test3() {
   checkString(JS('', '#.toString()', -0.0));
 }
 
-
 main() {
   test1();
   test2();
   test3();
 }