dart2js: run dartfmt on tests

tests/compiler/dart2js_native/native_null_frog_test.dart

 // Copyright (c) 2011, 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:_js_helper";
 import "package:expect/expect.dart";
 
 // Test for values of some basic types.
 
-
 @Native("A")
 class A {
-  returnNull() native;
-  returnUndefined() native;
-  returnEmptyString() native;
-  returnZero() native;
+  returnNull() native ;
+  returnUndefined() native ;
+  returnEmptyString() native ;
+  returnZero() native ;
 }
 
-A makeA() native;
+A makeA() native ;
 
 void setup() native """
 function A() {}
 A.prototype.returnNull = function() { return null; };
 A.prototype.returnUndefined = function() { return void 0; };
 A.prototype.returnEmptyString = function() { return ""; };
 A.prototype.returnZero = function() { return 0; };
 makeA = function(){return new A;};
 """;
 
-
 main() {
   setup();
   A a = makeA();
   Expect.equals(null, a.returnNull());
   Expect.equals(null, a.returnUndefined());
 
   Expect.equals('', a.returnEmptyString());
   Expect.isTrue(a.returnEmptyString().isEmpty);
   Expect.isTrue(a.returnEmptyString() is String);
 
   Expect.isTrue(a.returnZero() is int);
   Expect.equals(0, a.returnZero());
 }