Add onPlatformViewCreated to HtmlElementView (#84095)

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

@@ -345,6 +345,7 @@ class HtmlElementView extends StatelessWidget {
   const HtmlElementView({
     Key? key,
     required this.viewType,
+    this.onPlatformViewCreated,
   }) : assert(viewType != null),
        assert(kIsWeb, 'HtmlElementView is only available on Flutter Web.'),
        super(key: key);
@@ -354,6 +355,11 @@ class HtmlElementView extends StatelessWidget {
   /// A PlatformViewFactory for this type must have been registered.
   final String viewType;
 
+  /// Callback to invoke after the platform view has been created.
+  ///
+  /// May be null.
+  final PlatformViewCreatedCallback? onPlatformViewCreated;
+
   @override
   Widget build(BuildContext context) {
     return PlatformViewLink(
@@ -372,7 +378,10 @@ class HtmlElementView extends StatelessWidget {
   /// Creates the controller and kicks off its initialization.
   _HtmlElementViewController _createHtmlElementView(PlatformViewCreationParams params) {
     final _HtmlElementViewController controller = _HtmlElementViewController(params.id, viewType);
-    controller._initialize().then((_) { params.onPlatformViewCreated(params.id); });
+    controller._initialize().then((_) {
+      params.onPlatformViewCreated(params.id);
+      onPlatformViewCreated?.call(params.id);
+    });
     return controller;
   }
 }

packages/flutter/test/widgets/html_element_view_test.dart

@@ -37,6 +37,40 @@ void main() {
       );
     });
 
+    testWidgets('Create HTML view with PlatformViewCreatedCallback', (WidgetTester tester) async {
+      final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
+      final FakeHtmlPlatformViewsController viewsController = FakeHtmlPlatformViewsController();
+      viewsController.registerViewType('webview');
+
+      bool hasPlatformViewCreated = false;
+      void onPlatformViewCreatedCallBack(int id) {
+        hasPlatformViewCreated = true;
+      }
+
+      await tester.pumpWidget(
+        Center(
+          child: SizedBox(
+            width: 200.0,
+            height: 100.0,
+            child: HtmlElementView(
+              viewType: 'webview',
+              onPlatformViewCreated: onPlatformViewCreatedCallBack,
+            ),
+          ),
+        ),
+      );
+
+      // Check the onPlatformViewCreatedCallBack has been called.
+      expect(hasPlatformViewCreated, true);
+
+      expect(
+        viewsController.views,
+        unorderedEquals(<FakeHtmlPlatformView>[
+          FakeHtmlPlatformView(currentViewId + 1, 'webview'),
+        ]),
+      );
+    });
+
     testWidgets('Resize HTML view', (WidgetTester tester) async {
       final int currentViewId = platformViewsRegistry.getNextPlatformViewId();
       final FakeHtmlPlatformViewsController viewsController = FakeHtmlPlatformViewsController();