Stop using shadowThemeOnly:true in Theme.of().

@@ -341,7 +341,8 @@ class CupertinoScaffold extends StatefulWidget {
     assert(useRootNavigator != null);
     assert(enableDrag != null);
     assert(debugCheckHasMediaQuery(context));
-    final isCupertinoApp = Theme.of(context, shadowThemeOnly: true) == null;
+    final isCupertinoApp =
+        context.findAncestorWidgetOfExactType<CupertinoApp>() != null;
     var barrierLabel = '';
     if (!isCupertinoApp) {
       assert(debugCheckHasMaterialLocalizations(context));

@@ -39,7 +39,7 @@ Future<T> showMaterialModalBottomSheet<T>({
       elevation: elevation,
       shape: shape,
       clipBehavior: clipBehavior,
-      theme: Theme.of(context, shadowThemeOnly: true),
+      theme: Theme.of(context),
     ),
     secondAnimationController: secondAnimation,
     bounce: bounce,