fix stream pipe

com.unity.uiwidgets/Runtime/async/stream.cs

         Future<E> drain<E>(E futureValue) =>
             listen(null, cancelOnError: true).asFuture<E>(futureValue);
 
-        Stream<T> take(int count) {
+        public Stream<T> take(int count) {
             return new _TakeStream<T>(this, count);
         }
 

com.unity.uiwidgets/Runtime/async/stream_pipe.cs

             Action<T> onData, Action<object, string> onError, Action onDone, bool cancelOnError
         )
             : base(onData, onError, onDone, cancelOnError) {
+            this._stream = _stream;
             _subscription = _stream._source
                 .listen(_handleData, onError: _handleError, onDone: _handleDone);
         }
                 this, onData, onError, onDone, cancelOnError, _count);
         }
 
-        void _handleData(T inputEvent, _EventSink<T> sink) {
+        internal override void _handleData(T inputEvent, _EventSink<T> sink) {
             _StateStreamSubscription<T> subscription = (_StateStreamSubscription<T>) sink;
             int count = subscription._count;
             if (count > 0) {