unfork DDC's copy of most SDK libraries

pkg/dev_compiler/tool/input_sdk/lib/async/deferred_load.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.
-
-part of dart.async;
-
-/**
- * Indicates that loading of [libraryName] is deferred.
- *
- * This class is obsolete. Instead use the syntax:
- * import "library.dart" deferred as prefix;
- */
-@Deprecated("Dart sdk v. 1.8")
-class DeferredLibrary {
-  final String libraryName;
-  final String uri;
-
-  const DeferredLibrary(this.libraryName, {this.uri});
-
-  /**
-   * Ensure that [libraryName] has been loaded.
-   *
-   * If the library fails to load, the Future will complete with a
-   * DeferredLoadException.
-   */
-  external Future<Null> load();
-}
-
-/**
- * Thrown when a deferred library fails to load.
- */
-class DeferredLoadException implements Exception {
-  DeferredLoadException(String this._s);
-  String toString() => "DeferredLoadException: '$_s'";
-  final String _s;
-}