Dispose of animation controller in shared y axis demo (flutter#259)

Author: Renzo-Olivares

lib/codeviewer/code_segments.dart

@@ -31560,6 +31560,25 @@ class CodeSegments {
       TextSpan(style: codeStyle.baseStyle, text: '\u000a\u000a  '),
       TextSpan(style: codeStyle.keywordStyle, text: '@override'),
       TextSpan(style: codeStyle.baseStyle, text: '\u000a  '),
+      TextSpan(style: codeStyle.keywordStyle, text: 'void'),
+      TextSpan(style: codeStyle.baseStyle, text: ' dispose'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '()'),
+      TextSpan(style: codeStyle.baseStyle, text: ' '),
+      TextSpan(style: codeStyle.punctuationStyle, text: '{'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a    _controller'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'dispose'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '();'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a    '),
+      TextSpan(style: codeStyle.keywordStyle, text: 'super'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '.'),
+      TextSpan(style: codeStyle.baseStyle, text: 'dispose'),
+      TextSpan(style: codeStyle.punctuationStyle, text: '();'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a  '),
+      TextSpan(style: codeStyle.punctuationStyle, text: '}'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a\u000a  '),
+      TextSpan(style: codeStyle.keywordStyle, text: '@override'),
+      TextSpan(style: codeStyle.baseStyle, text: '\u000a  '),
       TextSpan(style: codeStyle.classStyle, text: 'Widget'),
       TextSpan(style: codeStyle.baseStyle, text: ' build'),
       TextSpan(style: codeStyle.punctuationStyle, text: '('),

lib/demos/reference/motion_demo_shared_y_axis_transition.dart

@@ -56,6 +56,12 @@ class _SharedYAxisTransitionDemoState extends State<SharedYAxisTransitionDemo>
     'J',
   ];
 
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
   @override
   Widget build(BuildContext context) {
     final localizations = GalleryLocalizations.of(context);