Add a flag to toggle navigator route update reporting (#60621)

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

@@ -1308,6 +1308,7 @@ class _WidgetsAppState extends State<WidgetsApp> with WidgetsBindingObserver {
           },
         onUnknownRoute: _onUnknownRoute,
         observers: widget.navigatorObservers,
+        reportsRouteUpdateToEngine: true,
       );
     }
 

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

@@ -1397,11 +1397,13 @@ class Navigator extends StatefulWidget {
     this.onGenerateRoute,
     this.onUnknownRoute,
     this.transitionDelegate = const DefaultTransitionDelegate<dynamic>(),
+    this.reportsRouteUpdateToEngine = false,
     this.observers = const <NavigatorObserver>[],
   }) : assert(pages != null),
        assert(onGenerateInitialRoutes != null),
        assert(transitionDelegate != null),
        assert(observers != null),
+       assert(reportsRouteUpdateToEngine != null),
        super(key: key);
 
   /// The list of pages with which to populate the history.
@@ -1497,6 +1499,22 @@ class Navigator extends StatefulWidget {
   /// will be primed.
   final RouteListFactory onGenerateInitialRoutes;
 
+  /// Whether this navigator should report route update message back to the
+  /// engine when the top-most route changes.
+  ///
+  /// If the property is set to true, this navigator automatically sends the
+  /// route update message to the engine when it detects top-most route changes.
+  /// The messages are used by the web engine to update the browser URL bar.
+  ///
+  /// If there are multiple navigators in the widget tree, at most one of them
+  /// can set this property to true (typically, the top-most one created from
+  /// the [WidgetsApp]). Otherwise, the web engine may receive multiple route
+  /// update messages from different navigators and fail to update the URL
+  /// bar.
+  ///
+  /// Defaults to false.
+  final bool reportsRouteUpdateToEngine;
+
   /// Push a named route onto the navigator that most tightly encloses the given
   /// context.
   ///
@@ -3244,12 +3262,16 @@ class NavigatorState extends State<Navigator> with TickerProviderStateMixin {
     _flushRouteAnnouncement();
 
     // Announces route name changes.
-    final _RouteEntry lastEntry = _history.lastWhere(_RouteEntry.isPresentPredicate, orElse: () => null);
+    if (widget.reportsRouteUpdateToEngine) {
+      final _RouteEntry lastEntry = _history.lastWhere(
+        _RouteEntry.isPresentPredicate, orElse: () => null);
       final String routeName = lastEntry?.route?.settings?.name;
       if (routeName != _lastAnnouncedRouteName) {
-      RouteNotificationMessages.maybeNotifyRouteChange(routeName, _lastAnnouncedRouteName);
+        RouteNotificationMessages.maybeNotifyRouteChange(
+          routeName, _lastAnnouncedRouteName);
         _lastAnnouncedRouteName = routeName;
       }
+    }
 
     // Lastly, removes the overlay entries of all marked entries and disposes
     // them.

packages/flutter/test/widgets/route_notification_messages_test.dart

@@ -103,6 +103,48 @@ void main() {
         ));
   });
 
+  testWidgets('Navigator does not report route name by default', (WidgetTester tester) async {
+    final List<MethodCall> log = <MethodCall>[];
+    SystemChannels.navigation.setMockMethodCallHandler((MethodCall methodCall) async {
+      log.add(methodCall);
+    });
+
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: Navigator(
+        pages: <Page<void>>[
+          TransitionBuilderPage<void>(
+            name: '/',
+            pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) => const Placeholder(),
+          ),
+        ],
+        onPopPage: (Route<void> route, void result) => false,
+      )
+    ));
+
+    expect(log, hasLength(0));
+
+    await tester.pumpWidget(Directionality(
+      textDirection: TextDirection.ltr,
+      child: Navigator(
+        pages: <Page<void>>[
+          TransitionBuilderPage<void>(
+            name: '/',
+            pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) => const Placeholder(),
+          ),
+          TransitionBuilderPage<void>(
+            name: '/abc',
+            pageBuilder: (BuildContext context, Animation<double> animation, Animation<double> secondaryAnimation) => const Placeholder(),
+          ),
+        ],
+        onPopPage: (Route<void> route, void result) => false,
+      )
+    ));
+
+    await tester.pumpAndSettle();
+    expect(log, hasLength(0));
+  });
+
   testWidgets('Replace should send platform messages', (WidgetTester tester) async {
     final Map<String, WidgetBuilder> routes = <String, WidgetBuilder>{
       '/': (BuildContext context) => OnTapPage(