Implement modular compilation

lib/src/runner/file_utils.dart

Index: lib/src/runner/file_utils.dart
diff --git a/lib/src/runner/file_utils.dart b/lib/src/runner/file_utils.dart
deleted file mode 100644
index f4e8c3a0053aec6164b0323ae6c76df7493e9049..0000000000000000000000000000000000000000
--- a/lib/src/runner/file_utils.dart
+++ /dev/null
@@ -1,16 +0,0 @@
-// 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.
-
-/// File-listing utils used by dartdevrun.
-
-import 'dart:async';
-import 'dart:io';
-
-Future<List<File>> listJsFiles(Directory dir) async {
-  var list = [];
-  await for (var file in dir.list(recursive: true, followLinks: true)) {
-    if (file is File && file.path.endsWith(".js")) list.add(file.absolute);
-  }
-  return list;
-}