dart2js: run dartfmt on tests

tests/compiler/dart2js_native/js_constant_test.dart

Index: tests/compiler/dart2js_native/js_constant_test.dart
diff --git a/tests/compiler/dart2js_native/js_constant_test.dart b/tests/compiler/dart2js_native/js_constant_test.dart
index 19b2e6f9f1fe6f3055310886213bb895ea5376a3..7658dc07f467aac57ec6134b74199485219b1e1a 100644
--- a/tests/compiler/dart2js_native/js_constant_test.dart
+++ b/tests/compiler/dart2js_native/js_constant_test.dart
@@ -20,8 +20,8 @@ import "package:expect/expect.dart";
 
 @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() {
@@ -36,7 +36,6 @@ test3() {
   checkString(JS('', '#.toString()', -0.0));
 }
 
-
 main() {
   test1();
   test2();