fix GestureDetector.onDoubleTapDown not getting called (#108056)

packages/flutter/lib/src/widgets/gesture_detector.dart

@@ -1047,7 +1047,9 @@ class GestureDetector extends StatelessWidget {
       );
     }
 
-    if (onDoubleTap != null) {
+    if (onDoubleTap != null ||
+        onDoubleTapDown != null ||
+        onDoubleTapCancel != null) {
       gestures[DoubleTapGestureRecognizer] = GestureRecognizerFactoryWithHandlers<DoubleTapGestureRecognizer>(
         () => DoubleTapGestureRecognizer(debugOwner: this, supportedDevices: supportedDevices),
         (DoubleTapGestureRecognizer instance) {

packages/flutter/test/widgets/gesture_detector_test.dart

@@ -922,6 +922,54 @@ void main() {
     expect(panDelta, isNull);
     expect(didEndPan, isFalse);
   });
+
+  group('DoubleTap', () {
+    testWidgets('onDoubleTap is called even if onDoubleTapDown has not been not provided', (WidgetTester tester) async {
+      final List<String> log = <String>[];
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: GestureDetector(
+            onDoubleTap: () => log.add('double-tap'),
+            child: Container(
+              width: 100.0,
+              height: 100.0,
+              color: const Color(0xFF00FF00),
+            ),
+          ),
+        ),
+      );
+
+      await tester.tap(find.byType(Container));
+      await tester.pump(kDoubleTapMinTime);
+      await tester.tap(find.byType(Container));
+      await tester.pumpAndSettle();
+      expect(log, <String>['double-tap']);
+    });
+
+    testWidgets('onDoubleTapDown is called even if onDoubleTap has not been not provided', (WidgetTester tester) async {
+      final List<String> log = <String>[];
+      await tester.pumpWidget(
+        Directionality(
+          textDirection: TextDirection.ltr,
+          child: GestureDetector(
+            onDoubleTapDown: (_) => log.add('double-tap-down'),
+            child: Container(
+              width: 100.0,
+              height: 100.0,
+              color: const Color(0xFF00FF00),
+            ),
+          ),
+        ),
+      );
+
+      await tester.tap(find.byType(Container));
+      await tester.pump(kDoubleTapMinTime);
+      await tester.tap(find.byType(Container));
+      await tester.pumpAndSettle();
+      expect(log, <String>['double-tap-down']);
+    });
+  });
 }
 
 class _EmptySemanticsGestureDelegate extends SemanticsGestureDelegate {