Change the zone that late-added stream subscription callbacks are registered in.

sdk/lib/async/stream_impl.dart

 // Copyright (c) 2012, 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;
 
 /** Abstract and private interface for a place to put events. */
 abstract class _EventSink<T> {
   void _add(T data);
   void _addError(Object error, StackTrace stackTrace);
@@ skipping 126 matching lines @@
     assert(_isCanceled);
     _PendingEvents events = _pending;
     _pending = null;
     return events;
   }
 
   // StreamSubscription interface.
 
   void onData(void handleData(T event)) {
     if (handleData == null) handleData = _nullDataHandler;
-    _onData = Zone.current.registerUnaryCallback(handleData);
+    _onData = _zone.registerUnaryCallback(handleData);
   }
 
   void onError(Function handleError) {
     if (handleError == null) handleError = _nullErrorHandler;
-    _onError = _registerErrorHandler(handleError, Zone.current);
+    _onError = _registerErrorHandler(handleError, _zone);
   }
 
   void onDone(void handleDone()) {
     if (handleDone == null) handleDone = _nullDoneHandler;
-    _onDone = Zone.current.registerCallback(handleDone);
+    _onDone = _zone.registerCallback(handleDone);
   }
 
   void pause([Future resumeSignal]) {
     if (_isCanceled) return;
     bool wasPaused = _isPaused;
     bool wasInputPaused = _isInputPaused;
     // Increment pause count and mark input paused (if it isn't already).
     _state = (_state + _STATE_PAUSE_COUNT) | _STATE_INPUT_PAUSED;
     if (resumeSignal != null) resumeSignal.whenComplete(resume);
     if (!wasPaused && _pending != null) _pending.cancelSchedule();
@@ skipping 860 matching lines @@
       _Future<bool> hasNext = _futureOrPrefetch;
       _clear();
       hasNext._complete(false);
       return;
     }
     _subscription.pause();
     _futureOrPrefetch = null;
     _state = _STATE_EXTRA_DONE;
   }
 }