Allow Navigator to inherit traversal policy from parent. (#110818)

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

@@ -5235,6 +5235,7 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin, Res
         child: AbsorbPointer(
           absorbing: false, // it's mutated directly by _cancelActivePointers above
           child: FocusTraversalGroup(
+            policy: FocusTraversalGroup.maybeOf(context),
             child: Focus(
               focusNode: focusNode,
               autofocus: true,

packages/flutter/test/widgets/navigator_test.dart

@@ -3775,8 +3775,7 @@ void main() {
     expect(focusNode.hasFocus, true);
   });
 
-  testWidgets('Navigator does not request focus if requestFocus is false',
-          (WidgetTester tester) async {
+  testWidgets('Navigator does not request focus if requestFocus is false', (WidgetTester tester) async {
     final GlobalKey navigatorKey = GlobalKey();
     final GlobalKey innerKey = GlobalKey();
     final Map<String, Widget> routes = <String, Widget>{
@@ -3873,6 +3872,49 @@ void main() {
     await tester.pumpWidget(Container(child: build(key)));
     observer._checkInvocations(<Symbol>[#navigator, #navigator]);
   });
+
+  testWidgets("Navigator doesn't override FocusTraversalPolicy of ancestors", (WidgetTester tester) async {
+    FocusTraversalPolicy? policy;
+    await tester.pumpWidget(
+      TestDependencies(
+        child: FocusTraversalGroup(
+          policy: WidgetOrderTraversalPolicy(),
+          child: Navigator(
+            onGenerateRoute: (RouteSettings settings) {
+              return PageRouteBuilder<void>(
+                settings: settings,
+                pageBuilder: (BuildContext context, Animation<double> __, Animation<double> ___) {
+                  policy = FocusTraversalGroup.of(context);
+                  return const SizedBox();
+                },
+              );
+            },
+          ),
+        ),
+      ),
+    );
+    expect(policy, isA<WidgetOrderTraversalPolicy>());
+  });
+
+  testWidgets('Navigator inserts ReadingOrderTraversalPolicy if no ancestor has a policy', (WidgetTester tester) async {
+    FocusTraversalPolicy? policy;
+    await tester.pumpWidget(
+      TestDependencies(
+        child: Navigator(
+          onGenerateRoute: (RouteSettings settings) {
+            return PageRouteBuilder<void>(
+              settings: settings,
+              pageBuilder: (BuildContext context, Animation<double> __, Animation<double> ___) {
+                policy = FocusTraversalGroup.of(context);
+                return const SizedBox();
+              },
+            );
+          },
+        ),
+      ),
+    );
+    expect(policy, isA<ReadingOrderTraversalPolicy>());
+  });
 }
 
 typedef AnnouncementCallBack = void Function(Route<dynamic>?);