Flutter Web App: adds a11y semantic attributes to slider (flutter#151985)

added Semantics wrapper over slider to add appropriate a11y semantic attributes to slider

Before: https://screenshot.googleplex.com/8jmDh3RSB3oG5Z2
After: https://screenshot.googleplex.com/7Z4FdVgwcC4ZQxm

fixes b/340638215

Author: DBowen33

dev/a11y_assessments/lib/use_cases/slider.dart

@@ -27,6 +27,7 @@ class MainWidget extends StatefulWidget {
 
 class MainWidgetState extends State<MainWidget> {
   double currentSliderValue = 20;
+  static const String accessibilityLabel = 'Accessibility Test Slider';
 
   @override
   Widget build(BuildContext context) {
@@ -36,16 +37,19 @@ class MainWidgetState extends State<MainWidget> {
         title: const Text('Slider'),
       ),
       body: Center(
-        child: Slider(
-          value: currentSliderValue,
-          max: 100,
-          divisions: 5,
-          label: currentSliderValue.round().toString(),
-          onChanged: (double value) {
-            setState(() {
-              currentSliderValue = value;
-            });
-          },
+        child: Semantics(
+          label: accessibilityLabel,
+          child: Slider(
+            value: currentSliderValue,
+            max: 100,
+            divisions: 5,
+            label: currentSliderValue.round().toString(),
+            onChanged: (double value) {
+              setState(() {
+                currentSliderValue = value;
+              });
+            },
+          ),
         ),
       ),
     );

dev/a11y_assessments/test/slider_test.dart

@@ -19,4 +19,9 @@ void main() {
     final MainWidgetState state = tester.state<MainWidgetState>(find.byType(MainWidget));
     expect(state.currentSliderValue, 60);
   });
+  testWidgets('slider semantics wrapper exists', (WidgetTester tester) async {
+    await pumpsUseCase(tester, SliderUseCase());
+    final Finder semanticsWidget = find.bySemanticsLabel('Accessibility Test Slider');
+    expect(semanticsWidget, findsOneWidget);
+  });
 }