anchor.diff:  
     void disposeInternal(){
       super.disposeInternal();
  -    _updatedEventHandle.dispose();
       _invalidatedEventHandle.dispose();
     }
   
  
positive.code: 
    ElementParent get parent => _parent;
  
    EventRoot<EventArgs> get updated => _updatedEventHandle;
  
    EventRoot<EventArgs> get invalidated => _invalidatedEventHandle;
  
    AffineTransform getTransform() {
  
negative.code: abstract class PElement extends AttachableObject {
    final List<AffineTransform> _transforms = new List<AffineTransform>();
    final bool cacheEnabled;
    final EventHandle<EventArgs> _invalidatedEventHandle = new EventHandle<EventArgs>();
    CanvasElement _cacheCanvas;
  
  