Add flutter_web samples (#75)

web/charts/common/test/chart/layout/layout_manager_impl_test.dart

@@ -0,0 +1,48 @@
+// 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:charts_common/src/chart/layout/layout_config.dart';
+import 'package:charts_common/src/chart/layout/layout_manager_impl.dart';
+
+import 'package:test/test.dart';
+
+void main() {
+  test('default layout', () {
+    var layout = LayoutManagerImpl();
+    layout.measure(400, 300);
+
+    expect(layout.marginTop, equals(0));
+    expect(layout.marginRight, equals(0));
+    expect(layout.marginBottom, equals(0));
+    expect(layout.marginLeft, equals(0));
+  });
+
+  test('all fixed margin', () {
+    var layout = LayoutManagerImpl(
+      config: LayoutConfig(
+        topSpec: MarginSpec.fixedPixel(12),
+        rightSpec: MarginSpec.fixedPixel(11),
+        bottomSpec: MarginSpec.fixedPixel(10),
+        leftSpec: MarginSpec.fixedPixel(9),
+      ),
+    );
+    layout.measure(400, 300);
+
+    expect(layout.marginTop, equals(12));
+    expect(layout.marginRight, equals(11));
+    expect(layout.marginBottom, equals(10));
+    expect(layout.marginLeft, equals(9));
+  });
+}