_YearPicker should dispose ScrollController and MaterialSatesController. (#134393)

Author: polina-c

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

@@ -1147,7 +1147,8 @@ class YearPicker extends StatefulWidget {
 }
 
 class _YearPickerState extends State<YearPicker> {
-  late ScrollController _scrollController;
+  ScrollController? _scrollController;
+  final MaterialStatesController _statesController = MaterialStatesController();
 
   // The approximate number of years necessary to fill the available space.
   static const int minYears = 18;
@@ -1158,11 +1159,18 @@ class _YearPickerState extends State<YearPicker> {
     _scrollController = ScrollController(initialScrollOffset: _scrollOffsetForYear(widget.selectedDate ?? widget.firstDate));
   }
 
+  @override
+  void dispose() {
+    _scrollController?.dispose();
+    _statesController.dispose();
+    super.dispose();
+  }
+
   @override
   void didUpdateWidget(YearPicker oldWidget) {
     super.didUpdateWidget(oldWidget);
     if (widget.selectedDate != oldWidget.selectedDate && widget.selectedDate != null) {
-      _scrollController.jumpTo(_scrollOffsetForYear(widget.selectedDate!));
+      _scrollController!.jumpTo(_scrollOffsetForYear(widget.selectedDate!));
     }
   }
 
@@ -1255,10 +1263,11 @@ class _YearPickerState extends State<YearPicker> {
         assert(date.year == widget.lastDate.year);
         date = DateTime(year, widget.lastDate.month);
       }
+      _statesController.value = states;
       yearItem = InkWell(
         key: ValueKey<int>(year),
         onTap: () => widget.onChanged(date),
-        statesController: MaterialStatesController(states),
+        statesController: _statesController,
         overlayColor: overlayColor,
         child: yearItem,
       );

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

@@ -57,8 +57,6 @@ typedef ScrollControllerCallback = void Function(ScrollPosition position);
 ///    listen to scrolling occur without using a [ScrollController].
 class ScrollController extends ChangeNotifier {
   /// Creates a controller for a scrollable widget.
-  ///
-  /// The values of `initialScrollOffset` and `keepScrollOffset` must not be null.
   ScrollController({
     double initialScrollOffset = 0.0,
     this.keepScrollOffset = true,

packages/flutter/test/material/calendar_date_picker_test.dart

@@ -5,6 +5,7 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 import 'feedback_tester.dart';
 
@@ -211,7 +212,7 @@ void main() {
       expect(selectedDate, equals(DateTime(2018, DateTime.january, 4)));
     });
 
-    testWidgets('Changing year for february 29th', (WidgetTester tester) async {
+    testWidgetsWithLeakTracking('Changing year for february 29th', (WidgetTester tester) async {
       DateTime? selectedDate;
       await tester.pumpWidget(calendarDatePicker(
         initialDate: DateTime(2020, DateTime.february, 29),
@@ -230,7 +231,7 @@ void main() {
       expect(selectedDate, equals(DateTime(2020, DateTime.february, 28)));
     });
 
-    testWidgets('Changing year does not change the month', (WidgetTester tester) async {
+    testWidgetsWithLeakTracking('Changing year does not change the month', (WidgetTester tester) async {
       DateTime? displayedMonth;
       await tester.pumpWidget(calendarDatePicker(
         initialDate: DateTime(2016, DateTime.january, 15),