Move dart2jslib parts into separate libraries.

tests/compiler/dart2js/simple_inferrer_postfix_prefix_test.dart

Index: tests/compiler/dart2js/simple_inferrer_postfix_prefix_test.dart
diff --git a/tests/compiler/dart2js/simple_inferrer_postfix_prefix_test.dart b/tests/compiler/dart2js/simple_inferrer_postfix_prefix_test.dart
index 20503548b95c9d8b375dd0c7e035512297d38808..c26104d34f6bbf40d0df9dcc95fe457d66326bea 100644
--- a/tests/compiler/dart2js/simple_inferrer_postfix_prefix_test.dart
+++ b/tests/compiler/dart2js/simple_inferrer_postfix_prefix_test.dart
@@ -2,10 +2,10 @@
 // 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:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
-import "package:async_helper/async_helper.dart";
+
 import 'compiler_helper.dart';
-import 'parser_helper.dart';
 import 'type_mask_test_helper.dart';
 
 const String TEST = """