Revert "Fix ExpansionTile shows children background when expanded" (#108844)

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

@@ -10,7 +10,6 @@ import 'expansion_tile_theme.dart';
 import 'icons.dart';
 import 'list_tile.dart';
 import 'list_tile_theme.dart';
-import 'material.dart';
 import 'theme.dart';
 
 const Duration _kExpand = Duration(milliseconds: 200);
@@ -433,13 +432,11 @@ class _ExpansionTileState extends State<ExpansionTile> with SingleTickerProvider
       offstage: closed,
       child: TickerMode(
         enabled: !closed,
-        child: Material(
-          child: Padding(
-            padding: widget.childrenPadding ?? expansionTileTheme.childrenPadding ?? EdgeInsets.zero,
-            child: Column(
-              crossAxisAlignment: widget.expandedCrossAxisAlignment ?? CrossAxisAlignment.center,
-              children: widget.children,
-            ),
+        child: Padding(
+          padding: widget.childrenPadding ?? expansionTileTheme.childrenPadding ?? EdgeInsets.zero,
+          child: Column(
+            crossAxisAlignment: widget.expandedCrossAxisAlignment ?? CrossAxisAlignment.center,
+            children: widget.children,
           ),
         ),
       ),

packages/flutter/test/material/expansion_tile_test.dart

@@ -5,8 +5,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
 
-import '../rendering/mock_canvas.dart';
-
 class TestIcon extends StatefulWidget {
   const TestIcon({super.key});
 
@@ -483,51 +481,6 @@ void main() {
     expect(columnRect.bottom, paddingRect.bottom - 4);
   });
 
-  testWidgets('ExpansionTile adds a Material widget above its children when expanded', (WidgetTester tester) async {
-    // Regression test for https://github.com/flutter/flutter/issues/107030
-    const Color childColor = Color(0xff4caf50);
-
-    await tester.pumpWidget(
-      const MaterialApp(
-        home: Material(
-          child: Center(
-            child: ExpansionTile(
-              title: Text('title'),
-              childrenPadding: EdgeInsets.fromLTRB(10, 8, 12, 4),
-              children: <Widget>[
-                ListTile(tileColor: childColor),
-              ],
-            ),
-          ),
-        ),
-      ),
-    );
-
-    final Finder rootMaterialFinder = find.ancestor(
-      of: find.byType(ExpansionTile),
-      matching: find.byType(Material),
-    );
-
-    final Finder expansionTileMaterialFinder = find.descendant(
-      of: find.byType(ExpansionTile),
-      matching: find.byType(Material),
-    );
-
-    // ExpansionTile should not add a Material widget when it is not expanded
-    expect(expansionTileMaterialFinder, findsNothing);
-
-    // Expand
-    await tester.tap(find.text('title'));
-    await tester.pumpAndSettle();
-
-    // ExpansionTile adds a Material widget when it is expanded
-    expect(expansionTileMaterialFinder, findsOneWidget);
-
-    // Child color is painted on the inner Material widget
-    expect(rootMaterialFinder, isNot(paints..path()..path(color: childColor)));
-    expect(expansionTileMaterialFinder, paints..path(color: childColor));
-  });
-
   testWidgets('ExpansionTile.collapsedBackgroundColor', (WidgetTester tester) async {
     const Key expansionTileKey = Key('expansionTileKey');
     const Color backgroundColor = Colors.red;