relayout active ListWheelScrollView children every performLayout (#124476)

during performLayout, active children's constraints were updated, but they weren't laid out again w.r.t their parent (ListWheelScrollView).

Fixes #123497

Author: werainkhatri

packages/flutter/lib/src/rendering/list_wheel_viewport.dart

@@ -763,8 +763,9 @@ class RenderListWheelViewport
 
     // Relayout all active children.
     RenderBox? child = firstChild;
+    int index = currentFirstIndex;
     while (child != null) {
-      child.layout(childConstraints, parentUsesSize: true);
+      _layoutChild(child, childConstraints, index++);
       child = childAfter(child);
     }
 

packages/flutter/test/widgets/list_wheel_scroll_view_test.dart

@@ -604,6 +604,41 @@ void main() {
       // centered.
       expect(viewport.childCount, 13);
     });
+
+    testWidgets('Active children are laid out with correct offset', (WidgetTester tester) async {
+      // Regression test for https://github.com/flutter/flutter/issues/123497
+      Future<void> buildWidget(double width) async {
+        return tester.pumpWidget(
+          Directionality(
+            textDirection: TextDirection.ltr,
+            child: ListWheelScrollView(
+              itemExtent: 100.0,
+              children: <Widget>[
+                SizedBox(
+                  width: width,
+                  child: const Center(child: Text('blah')),
+                ),
+              ],
+            ),
+          ),
+        );
+      }
+
+      double getSizedBoxWidth() => tester.getSize(find.byType(SizedBox)).width;
+      double getSizedBoxCenterX() => tester.getCenter(find.byType(SizedBox)).dx;
+
+      await buildWidget(200.0);
+      expect(getSizedBoxWidth(), 200.0);
+      expect(getSizedBoxCenterX(), 400.0);
+
+      await buildWidget(100.0);
+      expect(getSizedBoxWidth(), 100.0);
+      expect(getSizedBoxCenterX(), 400.0);
+
+      await buildWidget(300.0);
+      expect(getSizedBoxWidth(), 300.0);
+      expect(getSizedBoxCenterX(), 400.0);
+    });
   });
 
   group('pre-transform viewport', () {