anchor.diff:        var percentage = 100 - (100 / (duration / left));
   
         // Clamp.
  -      if (percentage > 100)
  +      if (percentage > 100) {
           percentage = 100;
  -      else if (percentage < 0)
  +      } else if (percentage < 0) {
           percentage = 0;
  +      }
   
         onStep(this, percentage);
       }
  
positive.code: part of animation;
  
  class StyleAnimation extends Animation {
    Element element;
  
    Map<String, Object> toProperties = {};
    Map<String, Object> fromProperties = {};
    Map<String, Object> currentProperties = {};
    Map<String, String> units = {};
  
    /**
     * Properties are set asynchronously (due to getComputedStyle()).
  
negative.code:   }
  
    run() {
      if (_propertiesReady is! Future) {
        _setFromProperties();
      }
  
      // Start the animation when the properties are set.
      _propertiesReady.then((bool ready) {
  