anchor.diff:      }
       subscriptions.remove(element.hashCode);
     }
  +
     // references to the local mouse event handlers
     var _mouseDown;
     Map<int, StreamSubscription> _mouseDownSubscriptions = new Map();
  
positive.code:     // to prevent selection during drag
      event.preventDefault();
  
      //print("mouse down, enabled: $enabled");
      // TODO if(!_dragging)?
  
      // store the current target
      // TODO should we get the element explicitly from our own list?
      // TODO or is event.currentTarget safely the same?
  
negative.code: import "dart:async";
  import "package:logging/logging.dart";
  
  /// Function that determines if a drag should be allowed to start
  typedef bool AllowDragStart(DragHandler dragHandler, Element element, MouseEvent event);
  
  /// The event class that is sent with drag handler stream event updates
  