anchor.diff:      bool shutdown = (controller == null) || controller.isClosed;
       var cancelHandler = _onCancelHandler;
       if (cancelHandler != null) {
  -      _zone.runUnary(
  -          cancelHandler, new _BroadcastSubscriptionWrapper<T>(this));
  +      _zone.runUnary(cancelHandler, new _BroadcastSubscriptionWrapper<T>(this));
       }
       if (shutdown) {
         var subscription = _subscription;
  
positive.code:     _cancel();
      _state |= _STATE_WAIT_FOR_CANCEL;
      var cancelFuture = _cancelFuture;
      if (cancelFuture != null &&
          !identical(cancelFuture, Future._nullFuture)) {
        cancelFuture.whenComplete(sendDone);
      } else {
        sendDone();
  
negative.code:   bool _isPaused = false;
  
    _StreamIterator(final Stream<T> stream)
        : _stateData = stream {
      ArgumentError.checkNotNull(stream, "stream");
    }
  
    T get current {
      if (_subscription != null && _isPaused) {
  