Update stream iterator doc and add test.

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 1323 matching lines @@
 
   Stream<T> bind(Stream<S> stream);
 }
 
 /**
  * An [Iterable] like interface for the values of a [Stream].
  *
  * This wraps a [Stream] and a subscription on the stream. It listens
  * on the stream, and completes the future returned by [moveNext] when the
  * next value becomes available.
- *
- * NOTICE: This is a tentative design. This class may change.
  */
 abstract class StreamIterator<T> {
 
   /** Create a [StreamIterator] on [stream]. */
   factory StreamIterator(Stream<T> stream)
       // TODO(lrn): use redirecting factory constructor when type
       // arguments are supported.
       => new _StreamIteratorImpl<T>(stream);
 
   /**
@@ skipping 41 matching lines @@
 class _ControllerEventSinkWrapper<T> implements EventSink<T> {
   EventSink _sink;
   _ControllerEventSinkWrapper(this._sink);
 
   void add(T data) { _sink.add(data); }
   void addError(error, [StackTrace stackTrace]) {
     _sink.addError(error, stackTrace);
   }
   void close() { _sink.close(); }
 }