expose strong checker API, for use by analyzer_cli

lib/config.dart

-// Copyright (c) 2015, 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.
-
-/// Configuration of DDC rule set.
-library dev_compiler.config;
-
-// Options shared by the compiler and runtime.
-class TypeOptions {
-  // A list of non-nullable type names (e.g., 'int')
-  static const List<String> NONNULLABLE_TYPES = const <String>[];
-  final List<String> nonnullableTypes;
-
-  TypeOptions({this.nonnullableTypes: NONNULLABLE_TYPES});
-}
-
-List<String> optionsToList(String option,
-    {List<String> defaultValue: const <String>[]}) {
-  if (option == null) {
-    return defaultValue;
-  } else if (option.isEmpty) {
-    return <String>[];
-  } else {
-    return option.split(',');
-  }
-}