Remove redundant 'flex' prefixes on enum values.

sky/sdk/example/rendering/justify_content.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 'dart:sky';
 
 import 'package:sky/painting/text_style.dart';
 import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/flex.dart';
 import 'package:sky/rendering/object.dart';
@@ skipping 14 matching lines @@
     table.add(new RenderPadding(child: paragraph, padding: new EdgeDims.only(top: 20.0)));
     var row = new RenderFlex(direction: FlexDirection.horizontal);
     row.add(new RenderSolidColorBox(const Color(0xFFFFCCCC), desiredSize: new Size(80.0, 60.0)));
     row.add(new RenderSolidColorBox(const Color(0xFFCCFFCC), desiredSize: new Size(64.0, 60.0)));
     row.add(new RenderSolidColorBox(const Color(0xFFCCCCFF), desiredSize: new Size(160.0, 60.0)));
     row.justifyContent = justify;
     table.add(row);
     row.parentData.flex = 1;
   }
 
-  addRow(FlexJustifyContent.flexStart);
-  addRow(FlexJustifyContent.flexEnd);
+  addRow(FlexJustifyContent.start);
+  addRow(FlexJustifyContent.end);
   addRow(FlexJustifyContent.center);
   addRow(FlexJustifyContent.spaceBetween);
   addRow(FlexJustifyContent.spaceAround);
 
   RenderDecoratedBox root = new RenderDecoratedBox(
     decoration: new BoxDecoration(backgroundColor: const Color(0xFFFFFFFF)),
     child: new RenderPadding(child: table, padding: new EdgeDims.symmetric(vertical: 50.0))
   );
 
   new SkyBinding(root: root);
 }