[Gallery] Fix directory structure (#312)

gallery/lib/studies/rally/charts/vertical_fraction_bar.dart

@@ -0,0 +1,36 @@
+// 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/material.dart';
+
+class VerticalFractionBar extends StatelessWidget {
+  const VerticalFractionBar({this.color, this.fraction});
+
+  final Color color;
+  final double fraction;
+
+  @override
+  Widget build(BuildContext context) {
+    return LayoutBuilder(builder: (context, constraints) {
+      return SizedBox(
+        height: constraints.maxHeight,
+        width: 4,
+        child: Column(
+          children: [
+            SizedBox(
+              height: (1 - fraction) * constraints.maxHeight,
+              child: Container(
+                color: Colors.black,
+              ),
+            ),
+            SizedBox(
+              height: fraction * constraints.maxHeight,
+              child: Container(color: color),
+            ),
+          ],
+        ),
+      );
+    });
+  }
+}