anchor.diff:  // found in the LICENSE file.
   
   import 'dart:async';
  -import 'dart:ui' as ui;
  +import 'dart:ui' show Point, Offset;
   
   import 'arena.dart';
   import 'constants.dart';
  
positive.code:     _gestureMap[pointer]?.reject();
    }
  
    void _resolveTap(int pointer, _TapResolution resolution, ui.Point globalPosition) {
      _gestureMap.remove(pointer);
      if (resolution == _TapResolution.tap) {
        if (onTapUp != null)
  
negative.code:   cancel
  }
  
  /// TapGesture represents a full gesture resulting from a single tap sequence,
  /// as part of a [MultiTapGestureRecognizer]. Tap gestures are passive, meaning
  /// that they will not preempt any other arena member in play.
  class _TapGesture extends _TapTracker {
  
    _TapGesture({
      MultiTapGestureRecognizer gestureRecognizer,
      PointerInputEvent event
    }) : gestureRecognizer = gestureRecognizer,
         super(event: event, entry: GestureArena.instance.add(event.pointer, gestureRecognizer)) {
      startTrackingPointer(gestureRecognizer.router, handleEvent);
    }
  
    final MultiTapGestureRecognizer gestureRecognizer;
  
    bool _wonArena = false;
    Point _finalPosition;
  
    void handleEvent(PointerInputEvent event) {
      assert(event.pointer == pointer);
  