Use relative URIs for core library part-of statements.

sdk/lib/async/stream_transformers.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;
+part of "async.dart";
 
 /**
  * Wraps an [_EventSink] so it exposes only the [EventSink] interface.
  */
 class _EventSinkWrapper<T> implements EventSink<T> {
   _EventSink _sink;
   _EventSinkWrapper(this._sink);
 
   void add(T data) {
     _sink._add(data);
@@ skipping 307 matching lines @@
   StreamSubscription<T> listen(void onData(T event),
       {Function onError, void onDone(), bool cancelOnError}) {
     cancelOnError = identical(true, cancelOnError);
     StreamSubscription<T> result = _onListen(_stream, cancelOnError);
     result.onData(onData);
     result.onError(onError);
     result.onDone(onDone);
     return result;
   }
 }