Revert "Make StreamController be a StreamSink, not just an EventSink."

sdk/lib/async/stream.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;
 
 // -------------------------------------------------------------------
 // Core Stream types
 // -------------------------------------------------------------------
 
@@ skipping 907 matching lines @@
 
   StreamSubscription<T> listen(void onData(T value),
                                { void onError(error),
                                  void onDone(),
                                  bool cancelOnError }) {
     return _stream.listen(onData, onError: onError, onDone: onDone,
                           cancelOnError: cancelOnError);
   }
 }
 
+/**
+ * [EventSink] wrapper that only exposes the [EventSink] interface.
+ */
+class _EventSinkView<T> extends EventSink<T> {
+  final EventSink<T> _sink;
+
+  _EventSinkView(this._sink);
+
+  void add(T value) { _sink.add(value); }
+  void addError(error) { _sink.addError(error); }
+  void close() { _sink.close(); }
+}
+
 
 /**
  * The target of a [Stream.pipe] call.
  *
  * The [Stream.pipe] call will pass itself to this object, and then return
  * the resulting [Future]. The pipe should complete the future when it's
  * done.
  */
 abstract class StreamConsumer<S> {
   Future addStream(Stream<S> stream);
@@ skipping 295 matching lines @@
    *
    * If a [moveNext] call has been made, it will complete with `false` as value,
    * as will all further calls to [moveNext].
    *
    * If you need to stop listening for values before the stream iterator is
    * automatically closed, you must call [cancel] to ensure that the stream
    * is properly closed.
    */
   void cancel();
 }