Fix `SnackBar` material clip (#125622)

fixes https://github.com/flutter/flutter/issues/125619

### Before

![Screenshot 2023-04-27 at 14 08 05](https://user-images.githubusercontent.com/48603081/234853490-0a9c4e18-20aa-40f7-a6b0-efb278f515eb.png)

### After

![Screenshot 2023-04-27 at 14 00 44](https://user-images.githubusercontent.com/48603081/234853470-c69c20d3-124d-438a-9312-2d17492c5606.png)

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

@@ -728,6 +728,7 @@ class _SnackBarState extends State<SnackBar> {
       shape: shape,
       elevation: elevation,
       color: backgroundColor,
+      clipBehavior: widget.clipBehavior,
       child: Theme(
         data: effectiveTheme,
         child: accessibleNavigation || theme.useMaterial3

packages/flutter/test/material/snack_bar_test.dart

@@ -2857,6 +2857,50 @@ testWidgets('SnackBarAction backgroundColor works as a Color', (WidgetTester tes
       contains('disabledBackgroundColor must not be provided when background color is a MaterialStateColor'))
     );
   });
+
+  testWidgets('SnackBar material applies SnackBar.clipBehavior', (WidgetTester tester) async {
+    await tester.pumpWidget(
+      MaterialApp(
+        home: Scaffold(
+          body: Container(),
+        ),
+      ),
+    );
+
+    final ScaffoldMessengerState scaffoldMessengerState = tester.state(find.byType(ScaffoldMessenger));
+    scaffoldMessengerState.showSnackBar(
+      const SnackBar(content: Text('I am a snack bar.')),
+    );
+
+    await tester.pumpAndSettle(); // Have the SnackBar fully animate out.
+
+    Material material = tester.widget<Material>(
+      find.descendant(of: find.byType(SnackBar),
+      matching: find.byType(Material))
+    );
+
+    expect(material.clipBehavior, Clip.hardEdge);
+
+    scaffoldMessengerState.hideCurrentSnackBar(); // Hide the SnackBar.
+
+    await tester.pumpAndSettle(); // Have the SnackBar fully animate out.
+
+    scaffoldMessengerState.showSnackBar(
+      const SnackBar(
+        content: Text('I am a snack bar.'),
+        clipBehavior: Clip.antiAlias,
+      ),
+    );
+
+    await tester.pumpAndSettle(); // Have the SnackBar fully animate in.
+
+    material = tester.widget<Material>(
+      find.descendant(of: find.byType(SnackBar),
+      matching: find.byType(Material))
+    );
+
+    expect(material.clipBehavior, Clip.antiAlias);
+  });
 }
 
 /// Start test for "SnackBar dismiss test".