Fix leaking curved animation. (#146644)

Author: polina-c

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

@@ -1140,9 +1140,9 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
   double get _minPreferredTrackHeight => _sliderTheme.trackHeight!;
 
   final _SliderState _state;
-  late Animation<double> _overlayAnimation;
-  late Animation<double> _valueIndicatorAnimation;
-  late Animation<double> _enableAnimation;
+  late CurvedAnimation _overlayAnimation;
+  late CurvedAnimation _valueIndicatorAnimation;
+  late CurvedAnimation _enableAnimation;
   final TextPainter _labelPainter = TextPainter();
   late HorizontalDragGestureRecognizer _drag;
   late TapGestureRecognizer _tap;
@@ -1451,6 +1451,9 @@ class _RenderSlider extends RenderBox with RelayoutWhenSystemFontsChangeMixin {
     _drag.dispose();
     _tap.dispose();
     _labelPainter.dispose();
+    _enableAnimation.dispose();
+    _valueIndicatorAnimation.dispose();
+    _overlayAnimation.dispose();
     super.dispose();
   }
 

packages/flutter/test/painting/system_fonts_test.dart

@@ -10,6 +10,7 @@ import 'package:flutter/material.dart';
 import 'package:flutter/rendering.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:leak_tracker_flutter_testing/leak_tracker_flutter_testing.dart';
 
 Future<void> verifyMarkedNeedsLayoutDuringTransientCallbacksPhase(WidgetTester tester, RenderObject renderObject) async {
   assert(!renderObject.debugNeedsLayout);
@@ -189,7 +190,7 @@ void main() {
     expect(element.dirty, isTrue);
   }, skip: isBrowser);  // TODO(yjbanov): cupertino does not work on the Web yet: https://github.com/flutter/flutter/issues/41920
 
-  testWidgets('RangeSlider relayout upon system fonts changes', (WidgetTester tester) async {
+  testWidgets('RangeSlider relayout upon system fonts changes more than once', (WidgetTester tester) async {
     await tester.pumpWidget(
       MaterialApp(
         home: Material(
@@ -212,7 +213,10 @@ void main() {
     await verifyMarkedNeedsLayoutDuringTransientCallbacksPhase(tester, renderObject);
   });
 
-  testWidgets('Slider relayout upon system fonts changes', (WidgetTester tester) async {
+  testWidgets('Slider relayout upon system fonts changes',
+  // TODO(polina-c): remove when fixed https://github.com/flutter/flutter/issues/145600 [leak-tracking-opt-in]
+  experimentalLeakTesting: LeakTesting.settings.withTracked(classes: <String>['CurvedAnimation']),
+  (WidgetTester tester) async {
     await tester.pumpWidget(
       MaterialApp(
         home: Material(