Fix DataTable example not being scrollable (#131556)

dev/bots/check_code_samples.dart

@@ -292,7 +292,6 @@ final Set<String> _knownMissingTests = <String>{
   'examples/api/test/material/stepper/stepper.controls_builder.0_test.dart',
   'examples/api/test/material/stepper/stepper.0_test.dart',
   'examples/api/test/material/flexible_space_bar/flexible_space_bar.0_test.dart',
-  'examples/api/test/material/data_table/data_table.1_test.dart',
   'examples/api/test/material/data_table/data_table.0_test.dart',
   'examples/api/test/material/floating_action_button_location/standard_fab_location.0_test.dart',
   'examples/api/test/material/chip/deletable_chip_attributes.on_deleted.0_test.dart',

examples/api/lib/material/data_table/data_table.1.dart

@@ -30,13 +30,12 @@ class DataTableExample extends StatefulWidget {
 }
 
 class _DataTableExampleState extends State<DataTableExample> {
-  static const int numItems = 10;
+  static const int numItems = 20;
   List<bool> selected = List<bool>.generate(numItems, (int index) => false);
 
   @override
   Widget build(BuildContext context) {
-    return SizedBox(
-      width: double.infinity,
+    return SingleChildScrollView(
       child: DataTable(
         columns: const <DataColumn>[
           DataColumn(

examples/api/test/material/data_table/data_table.1_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_api_samples/material/data_table/data_table.1.dart' as example;
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  testWidgets('DataTable is scrollable', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      const example.DataTableExampleApp(),
+    );
+
+    expect(find.byType(SingleChildScrollView), findsOneWidget);
+
+    expect(tester.getTopLeft(find.text('Row 5')), const Offset(66.0, 366.0));
+
+    await tester.drag(find.byType(SingleChildScrollView), const Offset(0.0, -200.0));
+    await tester.pumpAndSettle();
+
+    expect(tester.getTopLeft(find.text('Row 5')), const Offset(66.0, 186.0));
+  });
+}

packages/flutter/lib/src/material/data_table.dart

@@ -357,6 +357,13 @@ class DataCell {
 /// [PaginatedDataTable] which automatically splits the data into
 /// multiple pages.
 ///
+/// ## Performance considerations when wrapping [DataTable] with [SingleChildScrollView]
+///
+/// Wrapping a [DataTable] with [SingleChildScrollView] is expensive as [SingleChildScrollView]
+/// mounts and paints the entire [DataTable] even when only some rows are visible. If scrolling in
+/// one direction is necessary, then consider using a [CustomScrollView], otherwise use [PaginatedDataTable]
+/// to split the data into smaller pages.
+///
 /// {@tool dartpad}
 /// This sample shows how to display a [DataTable] with three columns: name, age, and
 /// role. The columns are defined by three [DataColumn] objects. The table