First pass at build dependency graph for barback.

pkg/barback/lib/barback.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.
 
-// Test that deferred loading requires same library names.
+library barback;
 
 import 'dart:async';
+import 'dart:io';
 
-@lazy  /// 01: compile-time error
-import 'deferred_function_library.dart';
-
-const lazy = const DeferredLibrary('fisk');
-
-main() {
-}
+export 'src/asset.dart';
+export 'src/asset_id.dart';
+export 'src/asset_provider.dart';
+export 'src/errors.dart';
+export 'src/transform.dart' show Transform;
+export 'src/transformer.dart';