Add flutter_web samples (#75)

web/charts/example/lib/combo_chart/combo_gallery.dart

@@ -0,0 +1,57 @@
+// Copyright 2018 the Charts project authors. Please see the AUTHORS file
+// for details.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import 'package:flutter_web/material.dart';
+import '../gallery_scaffold.dart';
+import 'date_time_line_point.dart';
+import 'numeric_line_bar.dart';
+import 'numeric_line_point.dart';
+import 'ordinal_bar_line.dart';
+import 'scatter_plot_line.dart';
+
+List<GalleryScaffold> buildGallery() {
+  return [
+    new GalleryScaffold(
+      listTileIcon: new Icon(Icons.insert_chart),
+      title: 'Ordinal Combo Chart',
+      subtitle: 'Ordinal combo chart with bars and lines',
+      childBuilder: () => new OrdinalComboBarLineChart.withRandomData(),
+    ),
+    new GalleryScaffold(
+      listTileIcon: new Icon(Icons.show_chart),
+      title: 'Numeric Line Bar Combo Chart',
+      subtitle: 'Numeric combo chart with lines and bars',
+      childBuilder: () => new NumericComboLineBarChart.withRandomData(),
+    ),
+    new GalleryScaffold(
+      listTileIcon: new Icon(Icons.show_chart),
+      title: 'Numeric Line Points Combo Chart',
+      subtitle: 'Numeric combo chart with lines and points',
+      childBuilder: () => new NumericComboLinePointChart.withRandomData(),
+    ),
+    new GalleryScaffold(
+      listTileIcon: new Icon(Icons.show_chart),
+      title: 'Time Series Combo Chart',
+      subtitle: 'Time series combo chart with lines and points',
+      childBuilder: () => new DateTimeComboLinePointChart.withRandomData(),
+    ),
+    new GalleryScaffold(
+      listTileIcon: new Icon(Icons.scatter_plot),
+      title: 'Scatter Plot Combo Chart',
+      subtitle: 'Scatter plot combo chart with a line',
+      childBuilder: () => new ScatterPlotComboLineChart.withRandomData(),
+    ),
+  ];
+}