Fix listeners being added to subscription after onListen was called.

sdk/lib/async/stream_transformers.dart

Index: sdk/lib/async/stream_transformers.dart
diff --git a/sdk/lib/async/stream_transformers.dart b/sdk/lib/async/stream_transformers.dart
index e869486bd07b158caeb54a2f6a609927e9459e7c..0ed4117338172e065f79f3feb272ab3705611458 100644
--- a/sdk/lib/async/stream_transformers.dart
+++ b/sdk/lib/async/stream_transformers.dart
@@ -35,9 +35,12 @@ class _SinkTransformerStreamSubscription<S, T>
 
   _SinkTransformerStreamSubscription(Stream<S> source,
                                      _SinkMapper mapper,
+                                     void onData(T data),
+                                     Function onError,
+                                     void onDone(),
                                      bool cancelOnError)
       // We set the adapter's target only when the user is allowed to send data.
-      : super(cancelOnError) {
+      : super(onData, onError, onDone, cancelOnError) {
     _EventSinkWrapper<T> eventSink = new _EventSinkWrapper<T>(this);
     _transformerSink = mapper(eventSink);
     _subscription = source.listen(_handleData,
@@ -181,10 +184,7 @@ class _BoundSinkStream<S, T> extends Stream<T> {
                                  bool cancelOnError }) {
     cancelOnError = identical(true, cancelOnError);
     StreamSubscription<T> subscription = new _SinkTransformerStreamSubscription(
-        _stream, _sinkMapper, cancelOnError);
-    subscription.onData(onData);
-    subscription.onError(onError);
-    subscription.onDone(onDone);
+        _stream, _sinkMapper, onData, onError, onDone, cancelOnError);
     return subscription;
   }
 }