Move dart2jslib parts into separate libraries.

tests/compiler/dart2js/simple_inferrer_final_field_test.dart

 // Copyright (c) 2013, 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 '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 = """
 
 class A {
   final intField;
   final giveUpField1;
   final giveUpField2;
   final fieldParameter;
   A() : intField = 42, giveUpField1 = 'foo', giveUpField2 = 'foo';
@@ skipping 22 matching lines @@
     }
 
     checkFieldTypeInClass('A', 'intField', compiler.typesTask.uint31Type);
     checkFieldTypeInClass('A', 'giveUpField1',
         findTypeMask(compiler, 'Interceptor', 'nonNullSubclass'));
     checkFieldTypeInClass('A', 'giveUpField2',
         compiler.typesTask.dynamicType.nonNullable());
     checkFieldTypeInClass('A', 'fieldParameter', compiler.typesTask.uint31Type);
   }));
 }