Introduce RenderProxyBox and RenderSizedBox

sky/examples/raw/sector-layout.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 'package:sky/framework/app.dart';
 import 'package:sky/framework/layout2.dart';
 
 const double kTwoPi = 2 * math.PI;
@@ skipping 108 matching lines @@
     assert(deltaTheta != null);
     assert(parentData is SectorParentData);
 
     if (_decoration == null)
       return;
 
     if (_decoration.backgroundColor != null) {
       sky.Paint paint = new sky.Paint()..color = _decoration.backgroundColor;
       sky.Path path = new sky.Path();
       double outerRadius = (parentData.radius + deltaRadius);
-      sky.Rect outerBounds = new sky.Rect()..setLTRB(-outerRadius, -outerRadius, outerRadius, outerRadius);
+      sky.Rect outerBounds = new sky.Rect.fromLTRB(-outerRadius, -outerRadius, outerRadius, outerRadius);
       path.arcTo(outerBounds, deg(parentData.theta), deg(deltaTheta), true);
       double innerRadius = parentData.radius;
-      sky.Rect innerBounds = new sky.Rect()..setLTRB(-innerRadius, -innerRadius, innerRadius, innerRadius);
+      sky.Rect innerBounds = new sky.Rect.fromLTRB(-innerRadius, -innerRadius, innerRadius, innerRadius);
       path.arcTo(innerBounds, deg(parentData.theta + deltaTheta), deg(-deltaTheta), false);
       path.close();
       canvas.drawPath(path, paint);
     }
   }
 }
 
 class SectorChildListParentData extends SectorParentData with ContainerParentDataMixin<RenderSector> { }
 
 class RenderSectorWithChildren extends RenderDecoratedSector with ContainerRenderNodeMixin<RenderSector, SectorChildListParentData> {
@@ skipping 353 matching lines @@
   rootCircle.add(new RenderSolidColor(0xFF0000FF, desiredDeltaTheta: kTwoPi * 0.4));
   var stack = new RenderSectorSlice(padding: 2.0);
   stack.add(new RenderSolidColor(0xFFFFFF00, desiredDeltaRadius: 20.0));
   stack.add(new RenderSolidColor(0xFFFF9000, desiredDeltaRadius: 20.0));
   stack.add(new RenderSolidColor(0xFF00FF00));
   rootCircle.add(stack);
 
   var root = new RenderBoxToRenderSectorAdapter(innerRadius: 50.0, child: rootCircle);
   app = new AppView(root);
 }