Style guide says enum values should be lowerCamelCase.

sky/tests/raw/render_flex.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import '../resources/third_party/unittest/unittest.dart';
 import '../resources/unit.dart';
 import '../resources/display_list.dart';
 import 'dart:sky' as sky;
 import 'package:sky/framework/app.dart';
 import 'package:sky/framework/rendering/block.dart';
@@ skipping 24 matching lines @@
       decoration = new BoxDecoration(backgroundColor: backgroundColor);
   }
 }
 
 TestApp app;
 
 void main() {
   initUnit();
 
   test("should flex", () {
-    RenderFlex flexRoot = new RenderFlex(direction: FlexDirection.Vertical);
+    RenderFlex flexRoot = new RenderFlex(direction: FlexDirection.vertical);
 
     RenderDecoratedBox root = new RenderDecoratedBox(
       decoration: new BoxDecoration(backgroundColor: const sky.Color(0xFF000000)),
       child: flexRoot
     );
 
     void addFlexChildSolidColor(RenderFlex parent, sky.Color backgroundColor, { int flex: 0 }) {
       RenderSolidColor child = new RenderSolidColor(backgroundColor);
       parent.add(child);
       child.parentData.flex = flex;
@@ skipping 11 matching lines @@
     renderBlock.add(new RenderSolidColor(const sky.Color(0xFF00FF00), desiredSize: new sky.Size(100.0, 50.0)));
     renderBlock.add(new RenderSolidColor(const sky.Color(0x7700FFFF), desiredSize: new sky.Size(50.0, 100.0)));
 
     var renderDecoratedBlock = new RenderDecoratedBox(
       decoration: new BoxDecoration(backgroundColor: const sky.Color(0xFFFFFFFF)),
       child: renderBlock
     );
 
     flexRoot.add(new RenderPadding(padding: const EdgeDims.all(10.0), child: renderDecoratedBlock));
 
-    var row = new RenderFlex(direction: FlexDirection.Horizontal);
+    var row = new RenderFlex(direction: FlexDirection.horizontal);
 
     // Purple and blue cells
     addFlexChildSolidColor(row, const sky.Color(0x77FF00FF), flex: 1);
     addFlexChildSolidColor(row, const sky.Color(0xFF0000FF), flex: 2);
 
     var decoratedRow = new RenderDecoratedBox(
       decoration: new BoxDecoration(backgroundColor: const sky.Color(0xFF333333)),
       child: row
     );
 
     flexRoot.add(decoratedRow);
     decoratedRow.parentData.flex = 3;
     app = new TestApp(root);
 
     expect(root.size.width, equals(sky.view.width));
     expect(root.size.height, equals(sky.view.height));
     expect(renderBlock.size.width, equals(sky.view.width - 20.0));
 
   });
 }