Init licenses for test bindings (#81961)

dev/automated_tests/integration_test/license_expectation.txt

+[0-9]+:[0-9]+ [+]1: All tests passed!

dev/automated_tests/integration_test/license_test.dart

+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('Can show the license page', (WidgetTester tester) async {
+    await tester.pumpWidget(const TestApp());
+    await tester.pump();
+
+    final Finder button = find.byType(TextButton);
+
+    await tester.tap(button);
+    await tester.pumpAndSettle();
+
+    await tester.scrollUntilVisible(
+      // Dart should very definitely be in the licenses list.
+      find.text('dart'),
+      100,
+      maxScrolls: 200,
+    );
+
+    expect(find.text('dart'), findsOneWidget);
+  });
+}
+
+class TestApp extends StatelessWidget {
+  const TestApp({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return const MaterialApp(
+      home: ShowLicenseButton(),
+    );
+  }
+}
+
+class ShowLicenseButton extends StatelessWidget {
+  const ShowLicenseButton({Key? key}) : super(key: key);
+
+  @override
+  Widget build(BuildContext context) {
+    return TextButton(
+      onPressed: () => showLicensePage(context: context),
+      child: const Text(
+        'Show licenses',
+        key: Key('show-licenses'),
+      ),
+    );
+  }
+}

packages/flutter_test/lib/src/binding.dart

@@ -324,13 +324,6 @@ abstract class TestWidgetsFlutterBinding extends BindingBase
     }
   }
 
-  @override
-  // ignore: MUST_CALL_SUPER
-  void initLicenses() {
-    // Do not include any licenses, because we're a test, and the LICENSE file
-    // doesn't get generated for tests.
-  }
-
   @override
   BinaryMessenger createBinaryMessenger() {
     return TestDefaultBinaryMessenger(super.createBinaryMessenger());
@@ -927,6 +920,13 @@ class AutomatedTestWidgetsFlutterBinding extends TestWidgetsFlutterBinding {
     binding.mockFlutterAssets();
   }
 
+  @override
+  // ignore: MUST_CALL_SUPER
+  void initLicenses() {
+    // Do not include any licenses, because we're a test, and the LICENSE file
+    // doesn't get generated for tests.
+  }
+
   FakeAsync? _currentFakeAsync; // set in runTest; cleared in postTest
   Completer<void>? _pendingAsyncTasks;
 

packages/flutter_tools/test/integration.shard/test_test.dart

@@ -209,6 +209,10 @@ void main() {
     }
     expect(result.exitCode, 0);
   });
+
+  testWithoutContext('integration test can show the license page', () async {
+    return _testFile('license', automatedTestsDirectory, integrationTestDirectory, exitCode: isZero, extraArguments: integrationTestExtraArgs);
+  });
 }
 
 Future<void> _testFile(