[webview_flutter] Use a local web server for legacy web integration tests (#5956)

Use a local web server for the legacy test, just as for the non-legacy version.

Also updates the repo tooling to ensure that this test file is found, so it's run regardless of whether tests are run by directory or by individual path.

Part of flutter/flutter#95420

Author: stuartmorgan-g

packages/webview_flutter/webview_flutter_web/example/integration_test/legacy/webview_flutter_test.dart

@@ -4,22 +4,35 @@
 
 import 'dart:async';
 import 'dart:html' as html;
+import 'dart:io';
 
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:integration_test/integration_test.dart';
 import 'package:webview_flutter_web_example/legacy/web_view.dart';
 
-void main() {
+void main() async {
   IntegrationTestWidgetsFlutterBinding.ensureInitialized();
 
-  // URLs to navigate to in tests. These need to be URLs that we are confident will
-  // always be accessible, and won't do redirection. (E.g., just
-  // 'https://www.google.com/' will sometimes redirect traffic that looks
-  // like it's coming from a bot, which is true of these tests).
-  const String primaryUrl = 'https://flutter.dev/';
-  const String secondaryUrl = 'https://www.google.com/robots.txt';
+  const String primaryPage = 'first.txt';
+  const String secondaryPage = 'second.txt';
+  final HttpServer server =
+      await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
+  unawaited(server.forEach((HttpRequest request) {
+    if (request.uri.path == '/$primaryPage') {
+      request.response.writeln('Hello, world.');
+    }
+    if (request.uri.path == '/$secondaryPage') {
+      request.response.writeln('Another page.');
+    } else {
+      fail('unexpected request: ${request.method} ${request.uri}');
+    }
+    request.response.close();
+  }));
+  final String prefixUrl = 'http://localhost:${server.port}';
+  final String primaryUrl = '$prefixUrl/$primaryPage';
+  final String secondaryUrl = '$prefixUrl/$secondaryPage';
 
   testWidgets('initialUrl', (WidgetTester tester) async {
     final Completer<WebViewController> controllerCompleter =

script/tool/lib/src/drive_examples_command.dart

@@ -317,7 +317,8 @@ class DriveExamplesCommand extends PackageLoopingCommand {
         example.directory.childDirectory('integration_test');
 
     if (integrationTestDir.existsSync()) {
-      await for (final FileSystemEntity file in integrationTestDir.list()) {
+      await for (final FileSystemEntity file
+          in integrationTestDir.list(recursive: true)) {
         if (file is File && file.basename.endsWith('_test.dart')) {
           tests.add(file);
         }