anchor.diff:     * current position. Both are relative to the whole document (page coordinates).
      */
     void dragEnd(Point startPosition, Point position);
  -  
  -  Point _lastTranslate;
  -  bool _updating = false;
     
     /**
      * Sets the CSS transform translate of [avatar]. Uses requestAnimationFrame
  
positive.code:   void resetPointerEvents() {
      avatar.style.pointerEvents = null;
    }
  }
  
  
  
negative.code:     Point draggablePosition = pageOffset(draggable);
      
      // Set the initial position of avatar.
      setTopLeft(draggablePosition);
      
      // Ensure avatar has an absolute position.
      avatar.style.position = 'absolute';
  