Fix typo in Stream documentation.

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 30 matching lines @@
  *
  * *A broadcast stream* allows any number of listeners, and it fires
  * its events when they are ready, whether there are listeners or not.
  *
  * Broadcast streams are used for independent events/observers.
  *
  * If several listeners want to listen to a single subscription stream,
  * use [asBroadcastStream] to create a broadcast stream on top of the
  * non-broadcast stream.
  *
- * On either kind of stream, stream transformationss, such as [where] and
+ * On either kind of stream, stream transformations, such as [where] and
  * [skip], return the same type of stream as the one the method was called on,
  * unless otherwise noted.
  *
  * When an event is fired, the listener(s) at that time will receive the event.
  * If a listener is added to a broadcast stream while an event is being fired,
  * that listener will not receive the event currently being fired.
  * If a listener is canceled, it immediately stops receiving events.
  *
  * When the "done" event is fired, subscribers are unsubscribed before
  * receiving the event. After the event has been sent, the stream has no
@@ skipping 1596 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(); }
 }