fix: cuertino dialog action background blur effect (#25076)

packages/flutter/lib/src/cupertino/action_sheet.dart

@@ -1185,7 +1185,7 @@ class _RenderCupertinoAlertActions extends RenderBox
 
     final Path backgroundFillPath = Path()
       ..fillType = PathFillType.evenOdd
-      ..addRect(Rect.largest);
+      ..addRect(Rect.fromLTWH(0.0, 0.0, size.width, size.height));
 
     final Path pressedBackgroundFillPath = Path();
 

packages/flutter/lib/src/cupertino/dialog.dart

@@ -1578,7 +1578,7 @@ class _RenderCupertinoDialogActions extends RenderBox
     // Create the button backgrounds path and paint it.
     final Path backgroundFillPath = Path()
       ..fillType = PathFillType.evenOdd
-      ..addRect(Rect.largest)
+      ..addRect(Rect.fromLTWH(0.0, 0.0, size.width, size.height))
       ..addRect(verticalDivider);
 
     for (int i = 0; i < pressedButtonRects.length; i += 1) {
@@ -1616,7 +1616,7 @@ class _RenderCupertinoDialogActions extends RenderBox
 
     final Path backgroundFillPath = Path()
       ..fillType = PathFillType.evenOdd
-      ..addRect(Rect.largest);
+      ..addRect(Rect.fromLTWH(0.0, 0.0, size.width, size.height));
 
     final Path pressedBackgroundFillPath = Path();
 

packages/flutter/test/cupertino/dialog_test.dart

@@ -678,14 +678,15 @@ void main() {
     // the dividers also paints a white background the size of Rect.largest.
     // That background ends up being clipped by the containing ScrollView.
     //
-    // Here we test that the largest Rect is contained within the painted Path.
+    // Here we test that the Rect(0.0, 0.0, renderBox.size.width, renderBox.size.height)
+    // is contained within the painted Path.
     // We don't test for exclusion because for some reason the Path is reporting
     // that even points beyond Rect.largest are within the Path. That's not an
     // issue for our use-case, so we don't worry about it.
     expect(actionsSectionBox, paints..path(
       includes: <Offset>[
-        Offset(Rect.largest.left, Rect.largest.top),
-        Offset(Rect.largest.right, Rect.largest.bottom),
+        const Offset(0.0, 0.0),
+        Offset(actionsSectionBox.size.width, actionsSectionBox.size.height),
       ],
     ));
   });