Revert "Revert "Use native async/await support in pub.""

sdk/lib/_internal/pub_generated/lib/src/barback/source_directory.dart

Index: sdk/lib/_internal/pub_generated/lib/src/barback/source_directory.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/barback/source_directory.dart b/sdk/lib/_internal/pub_generated/lib/src/barback/source_directory.dart
deleted file mode 100644
index 9996ab9d1fa690e7995eba1f49b6a42c279b8926..0000000000000000000000000000000000000000
--- a/sdk/lib/_internal/pub_generated/lib/src/barback/source_directory.dart
+++ /dev/null
@@ -1,71 +0,0 @@
-// Copyright (c) 2014, 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.
-
-library pub.barback.source_directory;
-
-import 'dart:async';
-
-import 'package:watcher/watcher.dart';
-
-import 'asset_environment.dart';
-import 'barback_server.dart';
-
-/// A directory in the entrypoint package whose contents have been made
-/// available to barback and that are bound to a server.
-class SourceDirectory {
-  final AssetEnvironment _environment;
-
-  /// The relative directory path within the package.
-  final String directory;
-
-  /// The hostname to serve this directory on.
-  final String hostname;
-
-  /// The port to serve this directory on.
-  final int port;
-
-  /// The server bound to this directory.
-  ///
-  /// This is a future that will complete once [serve] has been called and the
-  /// server has been successfully spun up.
-  Future<BarbackServer> get server => _serverCompleter.future;
-  final _serverCompleter = new Completer<BarbackServer>();
-
-  /// The subscription to the [DirectoryWatcher] used to watch this directory
-  /// for changes.
-  ///
-  /// If the directory is not being watched, this will be `null`.
-  StreamSubscription<WatchEvent> watchSubscription;
-
-  SourceDirectory(this._environment, this.directory, this.hostname, this.port);
-
-  /// Binds a server running on [hostname]:[port] to this directory.
-  Future<BarbackServer> serve() {
-    return BarbackServer.bind(
-        _environment,
-        hostname,
-        port,
-        rootDirectory: directory).then((server) {
-      _serverCompleter.complete(server);
-      return server;
-    });
-  }
-
-  /// Removes the source directory from the build environment.
-  ///
-  /// Closes the server, removes the assets from barback, and stops watching it.
-  Future close() {
-    return server.then((server) {
-      var futures = [server.close()];
-
-      // Stop watching the directory.
-      if (watchSubscription != null) {
-        var cancel = watchSubscription.cancel();
-        if (cancel != null) futures.add(cancel);
-      }
-
-      return Future.wait(futures);
-    });
-  }
-}