anchor.diff:      // non checked mode since subscriptions will be null once the stream is
       // closed.
       assert(_subscriptions != null);
  -    StreamCallContextFunc contextFunc;
  +    Zone contextZone;
       if (_runInZone) {
  -      contextFunc = Zone.current.run;
  +      contextZone = Zone.current;
       }
       var sub = SimpleStreamSubscription<T>(
  -        this, onData, onDone, onError, cancelOnError, contextFunc);
  +        this, onData, onDone, onError, cancelOnError, contextZone);
       if (_subscriptions.isEmpty) {
         _subscriptions = [sub];
       } else {
  
positive.code: 
    void _add(T data) {
      if (_callback != null) {
        if (_contextFunc != null) {
          _contextFunc(() => _callback(data));
        } else {
          _callback(data);
        }
  
negative.code: 
    SimpleStream({bool isSync = false, bool runInZone = false})
        : _isSync = isSync,
          _runInZone = runInZone;
  
    SimpleStream.broadcast(
        {bool isSync = false,
  