Revert "Move dart2jslib parts into separate libraries."

tests/compiler/dart2js/field_codegen_test.dart

 // Copyright (c) 2012, 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.
 // Test that parameters keep their names in the output.
 
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 import 'compiler_helper.dart';
+import 'parser_helper.dart';
 
 const String TEST_NULL0 = r"""
 class A { static var x; }
 
 main() { return A.x; }
 """;
 
 const String TEST_NULL1 = r"""
 var x;
 
 main() { return x; }
 """;
 
 main() {
   asyncTest(() => compileAll(TEST_NULL0).then((generated) {
     Expect.isTrue(generated.contains("null"));
   }));
 
   asyncTest(() => compileAll(TEST_NULL1).then((generated) {
     Expect.isTrue(generated.contains("null"));
   }));
 }