Remove one more use of mirrors: Components now have to explicitly sync their fields.

sky/sdk/lib/framework/rendering/box.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:math' as math;
 import 'dart:sky' as sky;
 import 'dart:typed_data';
 import 'object.dart';
 import '../painting/shadows.dart';
 import 'package:vector_math/vector_math.dart';
@@ skipping 779 matching lines @@
     }
 
     return _cachedBackgroundPaint;
   }
 
   void paint(RenderObjectDisplayList canvas) {
     assert(size.width != null);
     assert(size.height != null);
 
     if (_decoration.backgroundColor != null || _decoration.boxShadow != null ||
-        _deocration.gradient != null) {
+        _decoration.gradient != null) {
       Rect rect = new Rect.fromLTRB(0.0, 0.0, size.width, size.height);
       if (_decoration.borderRadius == null)
         canvas.drawRect(rect, _backgroundPaint);
       else
         canvas.drawRRect(new sky.RRect()..setRectXY(rect, _decoration.borderRadius, _decoration.borderRadius), _backgroundPaint);
     }
 
     if (_decoration.border != null) {
       assert(_decoration.borderRadius == null); // TODO(abarth): Implement borders with border radius.
 
@@ skipping 278 matching lines @@
 
   void defaultPaint(RenderObjectDisplayList canvas) {
     RenderBox child = firstChild;
     while (child != null) {
       assert(child.parentData is ParentDataType);
       canvas.paintChild(child, child.parentData.position);
       child = child.parentData.nextSibling;
     }
   }
 }