Adding Rally App to Flutter Samples (#135)

material_studies/rally/lib/charts/vertical_fraction_bar.dart

@@ -0,0 +1,45 @@
+// Copyright 2019-present the Flutter authors. All Rights Reserved.
+//
+// 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/material.dart';
+import 'package:flutter/widgets.dart';
+
+class VerticalFractionBar extends StatelessWidget {
+  VerticalFractionBar({this.color, this.fraction});
+
+  final Color color;
+  final double fraction;
+
+  @override
+  Widget build(BuildContext context) {
+    return SizedBox(
+      height: 32.0,
+      width: 4.0,
+      child: Column(
+        children: [
+          SizedBox(
+            height: (1 - fraction) * 32.0,
+            child: Container(
+              color: Colors.black,
+            ),
+          ),
+          SizedBox(
+            height: fraction * 32.0,
+            child: Container(color: color),
+          ),
+        ],
+      ),
+    );
+  }
+}