[Gallery] Fix directory structure (#312)

gallery/lib/studies/rally/tabs/bills.dart

@@ -0,0 +1,38 @@
+// 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/widgets.dart';
+
+import 'package:gallery/l10n/gallery_localizations.dart';
+import 'package:gallery/layout/adaptive.dart';
+import 'package:gallery/studies/rally/charts/pie_chart.dart';
+import 'package:gallery/studies/rally/data.dart';
+import 'package:gallery/studies/rally/finance.dart';
+
+/// A page that shows a summary of bills.
+class BillsView extends StatefulWidget {
+  @override
+  _BillsViewState createState() => _BillsViewState();
+}
+
+class _BillsViewState extends State<BillsView>
+    with SingleTickerProviderStateMixin {
+  @override
+  Widget build(BuildContext context) {
+    List<BillData> items = DummyDataService.getBillDataList(context);
+    final dueTotal = sumBillDataPrimaryAmount(items);
+    return SingleChildScrollView(
+      child: Container(
+        padding: isDisplayDesktop(context) ? EdgeInsets.only(top: 24) : null,
+        child: FinancialEntityView(
+          heroLabel: GalleryLocalizations.of(context).rallyBillsDue,
+          heroAmount: dueTotal,
+          segments: buildSegmentsFromBillItems(items),
+          wholeAmount: dueTotal,
+          financialEntityCards: buildBillDataListViews(items, context),
+        ),
+      ),
+    );
+  }
+}