Style guide says enum values should be lowerCamelCase.

sky/sdk/lib/framework/fn2.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.
 
 library fn;
 
 import 'app.dart';
 import 'dart:async';
 import 'dart:collection';
 import 'dart:mirrors';
 import 'dart:sky' as sky;
 import 'package:vector_math/vector_math.dart';
 import 'reflect.dart' as reflect;
 import 'rendering/block.dart';
 import 'rendering/box.dart';
 import 'rendering/flex.dart';
 import 'rendering/object.dart';
 import 'rendering/paragraph.dart';
 import 'rendering/stack.dart';
 
 // final sky.Tracing _tracing = sky.window.tracing;
 
 final bool _shouldLogRenderDuration = false;
 final bool _shouldTrace = false;
 
-enum _SyncOperation { IDENTICAL, INSERTION, STATEFUL, STATELESS, REMOVAL }
+enum _SyncOperation { identical, insertion, stateful, stateless, removal }
 
 /*
  * All Effen nodes derive from UINode. All nodes have a _parent, a _key and
  * can be sync'd.
  */
 abstract class UINode {
   String _key;
   UINode _parent;
   UINode get parent => _parent;
   RenderObject root;
@@ skipping 51 matching lines @@
   void _traceSync(_SyncOperation op, String key) {
     if (!_shouldTrace)
       return;
 
     String opString = op.toString().toLowerCase();
     String outString = opString.substring(opString.indexOf('.') + 1);
     _trace('_sync($outString) $key');
   }
 
   void removeChild(UINode node) {
-    _traceSync(_SyncOperation.REMOVAL, node._key);
+    _traceSync(_SyncOperation.removal, node._key);
     node._remove();
   }
 
   // Returns the child which should be retained as the child of this node.
   UINode syncChild(UINode node, UINode oldNode, dynamic slot) {
     if (node == oldNode) {
-      _traceSync(_SyncOperation.IDENTICAL, node == null ? '*null*' : node._key);
+      _traceSync(_SyncOperation.identical, node == null ? '*null*' : node._key);
       return node; // Nothing to do. Subtrees must be identical.
     }
 
     if (node == null) {
       // the child in this slot has gone away
       removeChild(oldNode);
       return null;
     }
     assert(oldNode == null || node._key == oldNode._key);
 
     // TODO(rafaelw): This eagerly removes the old DOM. It may be that a
     // new component was built that could re-use some of it. Consider
     // syncing the new VDOM against the old one.
     if (oldNode != null && node._key != oldNode._key) {
       removeChild(oldNode);
     }
 
     if (node._willSync(oldNode)) {
-      _traceSync(_SyncOperation.STATEFUL, node._key);
+      _traceSync(_SyncOperation.stateful, node._key);
       oldNode._sync(node, slot);
       node._defunct = true;
       assert(oldNode.root is RenderObject);
       return oldNode;
     }
 
     assert(!node._defunct);
     node._parent = this;
 
     if (oldNode == null) {
-      _traceSync(_SyncOperation.INSERTION, node._key);
+      _traceSync(_SyncOperation.insertion, node._key);
     } else {
-      _traceSync(_SyncOperation.STATELESS, node._key);
+      _traceSync(_SyncOperation.stateless, node._key);
     }
     node._sync(oldNode, slot);
     if (oldNode != null)
       oldNode._defunct = true;
 
     assert(node.root is RenderObject);
     return node;
   }
 }
 
@@ skipping 483 matching lines @@
 
 class FlexContainer extends MultiChildRenderObjectWrapper {
   RenderFlex root;
   RenderFlex createNode() => new RenderFlex(direction: this.direction);
 
   final FlexDirection direction;
 
   FlexContainer({
     Object key,
     List<UINode> children,
-    this.direction: FlexDirection.Horizontal
+    this.direction: FlexDirection.horizontal
   }) : super(key: key, children: children);
 
   void syncRenderObject(UINode old) {
     super.syncRenderObject(old);
     root.direction = direction;
   }
 }
 
 class FlexExpandingChild extends ParentDataNode {
   FlexExpandingChild(UINode content, [int flex = 1])
@@ skipping 311 matching lines @@
     assert(root.parent is RenderView);
   }
 }
 
 class Text extends Component {
   Text(this.data) : super(key: '*text*');
   final String data;
   bool get interchangeable => true;
   UINode build() => new Paragraph(text: data);
 }