[web] Reland "Migrate Flutter Web to JS static interop - 14".

lib/web_ui/lib/src/engine/navigation/js_url_strategy.dart

@@ -29,6 +29,7 @@ typedef _HistoryMove = Future<void> Function(int count);
 /// bridge from the app to the engine.
 @JS()
 @anonymous
+@staticInterop
 abstract class JsUrlStrategy {
   /// Creates an instance of [JsUrlStrategy] from a bag of URL strategy
   /// functions.
@@ -41,7 +42,9 @@ abstract class JsUrlStrategy {
     required _StateOperation replaceState,
     required _HistoryMove go,
   });
+}
 
+extension JsUrlStrategyExtension on JsUrlStrategy {
   /// Adds a listener to the `popstate` event and returns a function that, when
   /// invoked, removes the listener.
   external ui.VoidCallback addPopStateListener(html.EventListener fn);

lib/web_ui/lib/src/engine/navigation/url_strategy.dart

@@ -5,6 +5,7 @@
 import 'dart:async';
 import 'dart:html' as html;
 
+import 'package:js/js.dart' as js;
 import 'package:ui/ui.dart' as ui;
 
 import 'js_url_strategy.dart';
@@ -156,7 +157,7 @@ class CustomUrlStrategy extends UrlStrategy {
 
   @override
   ui.VoidCallback addPopStateListener(html.EventListener fn) =>
-      delegate.addPopStateListener(fn);
+      delegate.addPopStateListener(js.allowInterop(fn));
 
   @override
   String getPath() => delegate.getPath();

lib/web_ui/test/window_test.dart

@@ -42,6 +42,29 @@ void testMain() {
     await window.resetHistory();
   });
 
+  test('window.defaultRouteName should work with JsUrlStrategy', () async {
+    dynamic state = <dynamic, dynamic>{};
+    final JsUrlStrategy jsUrlStrategy = JsUrlStrategy(
+        getPath: allowInterop(() => '/initial'),
+        getState: allowInterop(() => state),
+        addPopStateListener: allowInterop((html.EventListener listener) => () {}),
+        prepareExternalUrl: allowInterop((String value) => ''),
+        pushState: allowInterop((Object? newState, String title, String url) {
+          expect(newState is Map, true);
+        }),
+        replaceState: allowInterop((Object? newState, String title, String url) {
+          expect(newState is Map, true);
+          state = newState;
+        }),
+        go: allowInterop(([int? delta]) async {
+          expect(delta, -1);
+        }));
+    final CustomUrlStrategy strategy =
+        CustomUrlStrategy.fromJs(jsUrlStrategy);
+    await window.debugInitializeHistory(strategy, useSingle: true);
+    expect(window.defaultRouteName, '/initial');
+  });
+
   test('window.defaultRouteName should not change', () async {
     final TestUrlStrategy strategy = TestUrlStrategy.fromEntry(
       const TestHistoryEntry('initial state', null, '/initial'),