anchor.diff:            height: config.height,
             padding: config.padding,
             opacity: config.opacity,
  -          performance: _performance,
  +          animation: new CurvedAnimation(
  +            parent: _controller,
  +            curve: Curves.ease
  +          ),
             target: target,
             verticalOffset: config.verticalOffset,
             screenEdgeMargin: config.screenEdgeMargin,
  
positive.code:   }
  
    void resetShowTimer() {
      assert(_performance.status == PerformanceStatus.completed);
      assert(_entry != null);
      _timer = new Timer(config.showDuration, hideTooltip);
    }
  
negative.code:   void didUpdateConfig(Tooltip oldConfig) {
      super.didUpdateConfig(oldConfig);
      if (config.fadeDuration != oldConfig.fadeDuration)
        _controller.duration = config.fadeDuration;
      if (_entry != null &&
          (config.message != oldConfig.message ||
           config.backgroundColor != oldConfig.backgroundColor ||
  