move the calculator files around (#4112)

examples/flutter_gallery/lib/demo/all.dart

@@ -4,6 +4,7 @@
 
 export 'buttons_demo.dart';
 export 'cards_demo.dart';
+export 'calculator_demo.dart';
 export 'chip_demo.dart';
 export 'colors_demo.dart';
 export 'data_table_demo.dart';

examples/flutter_gallery/lib/calculator/interface.dart → examples/flutter_gallery/lib/demo/calculator_demo.dart

@@ -4,7 +4,7 @@
 
 import 'package:flutter/material.dart';
 
-import 'logic.dart';
+import 'calculator_logic.dart';
 
 class Calculator extends StatefulWidget {
   Calculator({Key key}) : super(key: key);

examples/flutter_gallery/lib/gallery/app.dart

@@ -5,7 +5,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/scheduler.dart' show timeDilation;
 
-import '../calculator/interface.dart';
 import '../demo/all.dart';
 import 'home.dart';
 

examples/flutter_gallery/lib/gallery/home.dart

@@ -5,7 +5,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/widgets.dart';
 
-import '../calculator/interface.dart';
 import '../demo/all.dart';
 import 'drawer.dart';
 import 'header.dart';

examples/flutter_gallery/test/calculator/logic.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:flutter_gallery/calculator/logic.dart';
+import 'package:flutter_gallery/demo/calculator_logic.dart';
 import 'package:test/test.dart';
 
 void main() {

examples/flutter_gallery/test/calculator/smoke_test.dart

@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:flutter_gallery/calculator/interface.dart';
 import 'package:flutter/material.dart';
+import 'package:flutter_gallery/demo/calculator_demo.dart';
 import 'package:flutter_test/flutter_test.dart';
 
 void main() {