[Gallery] Fix directory structure (#312)

gallery/lib/demos/cupertino/cupertino_switch_demo.dart

@@ -0,0 +1,47 @@
+// Copyright 2019 The Flutter team. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter/cupertino.dart';
+
+import 'package:gallery/l10n/gallery_localizations.dart';
+
+// BEGIN cupertinoSwitchDemo
+
+class CupertinoSwitchDemo extends StatefulWidget {
+  @override
+  _CupertinoSwitchDemoState createState() => _CupertinoSwitchDemoState();
+}
+
+class _CupertinoSwitchDemoState extends State<CupertinoSwitchDemo> {
+  bool _switchValue = false;
+
+  @override
+  Widget build(BuildContext context) {
+    return CupertinoPageScaffold(
+      navigationBar: CupertinoNavigationBar(
+        automaticallyImplyLeading: false,
+        middle: Text(
+          GalleryLocalizations.of(context).demoSelectionControlsSwitchTitle,
+        ),
+      ),
+      child: Center(
+        child: Semantics(
+          container: true,
+          label:
+              GalleryLocalizations.of(context).demoSelectionControlsSwitchTitle,
+          child: CupertinoSwitch(
+            value: _switchValue,
+            onChanged: (value) {
+              setState(() {
+                _switchValue = value;
+              });
+            },
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+// END