Fixes hot restart correctly reset the browser history

lib/web_ui/lib/src/engine/window.dart

@@ -32,6 +32,9 @@ class EngineFlutterWindow extends ui.SingletonFlutterWindow {
       _browserHistory =
           MultiEntriesBrowserHistory(urlStrategy: _customUrlStrategy);
     }
+    registerHotRestartListener(() {
+      window.resetHistory();
+    });
   }
 
   final Object _windowId;
@@ -86,12 +89,11 @@ class EngineFlutterWindow extends ui.SingletonFlutterWindow {
     }
   }
 
-  @visibleForTesting
-  Future<void> debugResetHistory() async {
+  Future<void> resetHistory() async {
     await _browserHistory?.tearDown();
     _browserHistory = null;
-
     // Reset the globals too.
+    _usingRouter = false;
     _isUrlStrategySet = false;
     _customUrlStrategy = null;
   }

lib/web_ui/test/engine/history_test.dart

@@ -48,7 +48,7 @@ void testMain() {
 
     tearDown(() async {
       spy.tearDown();
-      await window.debugResetHistory();
+      await window.resetHistory();
     });
 
     test('basic setup works', () async {
@@ -262,7 +262,7 @@ void testMain() {
 
     tearDown(() async {
       spy.tearDown();
-      await window.debugResetHistory();
+      await window.resetHistory();
     });
 
     test('basic setup works', () async {

lib/web_ui/test/engine/navigation_test.dart

@@ -28,7 +28,7 @@ void testMain() {
 
   tearDown(() async {
     _strategy = null;
-    await engine.window.debugResetHistory();
+    await engine.window.resetHistory();
   });
 
   test('Tracks pushed, replaced and popped routes', () async {

lib/web_ui/test/window_test.dart

@@ -33,7 +33,7 @@ void testMain() {
   });
 
   tearDown(() async {
-    await window.debugResetHistory();
+    await window.resetHistory();
     window = null;
   });