anchor.diff:  
     /// Delays the delivery of each non-error event from this stream by the given [duration].
     EventStream<T> delay(Duration duration) {
  -    return new EventStream<T>(new _DelayStream(this, duration));
  +    return _asEventStream(new _DelayStream(this, duration));
     }
   
     /// Returns a new stream that includes events and errors from only the latest stream
  
positive.code:   ///
    /// The returned stream will not throttle errors.
    EventStream<T> throttle(Duration duration) {
      return new EventStream<T>(new _ThrottleStream(this, duration));
    }
  
    /// Returns a [Property] where the first value will be the next value from this stream.
  
negative.code:   /// Returns a new stream that will begin forwarding events from this stream when the
    /// [future] completes.
    EventStream<T> skipUntil(Future future) {
      return _asEventStream(new _SkipUntilStream(this, future));
    }
  
    /// Returns a new stream that contains events from this stream until the [future]
    /// completes.
    EventStream<T> takeUntil(Future future) {
      return _asEventStream(new _TakeUntilStream(this, future));
    }
  
    /// Returns a new stream that upon forwarding an event from this stream, will ignore
  