Add dismiss action to modal barrier (#78808)

* Add dismiss action to modal barrier

* fix test

* fix another test

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

@@ -92,6 +92,11 @@ class ModalBarrier extends StatelessWidget {
     assert(platformSupportsDismissingBarrier != null);
     final bool semanticsDismissible = dismissible && platformSupportsDismissingBarrier;
     final bool modalBarrierSemanticsDismissible = barrierSemanticsDismissible ?? semanticsDismissible;
+
+    void handleDismiss() {
+      Navigator.maybePop(context);
+    }
+
     return BlockSemantics(
       child: ExcludeSemantics(
         // On Android, the back button is used to dismiss a modal. On iOS, some
@@ -100,12 +105,13 @@ class ModalBarrier extends StatelessWidget {
         child: _ModalBarrierGestureDetector(
           onDismiss: () {
             if (dismissible)
-              Navigator.maybePop(context);
+              handleDismiss();
             else
               SystemSound.play(SystemSoundType.alert);
           },
           child: Semantics(
             label: semanticsDismissible ? semanticsLabel : null,
+            onDismiss: semanticsDismissible ? handleDismiss : null,
             textDirection: semanticsDismissible && semanticsLabel != null ? Directionality.of(context) : null,
             child: MouseRegion(
               cursor: SystemMouseCursors.basic,

packages/flutter/test/cupertino/route_test.dart

@@ -1340,7 +1340,7 @@ void main() {
     await tester.pumpAndSettle();
 
     expect(semantics, includesNodeWith(
-      actions: <SemanticsAction>[SemanticsAction.tap],
+      actions: <SemanticsAction>[SemanticsAction.tap, SemanticsAction.dismiss],
       label: 'Dismiss',
     ));
     debugDefaultTargetPlatformOverride = null;

packages/flutter/test/widgets/modal_barrier_test.dart

@@ -378,7 +378,7 @@ void main() {
       children: <TestSemantics>[
         TestSemantics.rootChild(
           rect: TestSemantics.fullScreen,
-          actions: SemanticsAction.tap.index,
+          actions: <SemanticsAction>[SemanticsAction.tap, SemanticsAction.dismiss],
           label: 'Dismiss',
           textDirection: TextDirection.ltr,
         ),

packages/flutter/test/widgets/routes_test.dart

@@ -1544,7 +1544,7 @@ void main() {
               TestSemantics(
                 id: 5,
                 rect: TestSemantics.fullScreen,
-                actions: <SemanticsAction>[SemanticsAction.tap],
+                actions: <SemanticsAction>[SemanticsAction.tap, SemanticsAction.dismiss],
                 label: 'test label',
                 textDirection: TextDirection.ltr,
               ),