Split Size into Size and Offset.

sky/sdk/lib/rendering/stack.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 'box.dart';
 import 'object.dart';
 
 class StackParentData extends BoxParentData with ContainerParentDataMixin<RenderBox> {
@@ skipping 120 matching lines @@
         width = math.max(width, childSize.width);
         height = math.max(height, childSize.height);
       }
 
       child = parentData.nextSibling;
     }
 
     if (hasNonPositionedChildren)
       size = new Size(width, height);
     else
-      size = constraints.constrain(Size.infinite);
+      size = constraints.biggest;
 
     assert(!size.isInfinite);
     assert(size.width == constraints.constrainWidth(width));
     assert(size.height == constraints.constrainHeight(height));
 
     BoxConstraints innerConstraints = new BoxConstraints.loose(size);
 
     child = firstChild;
     while (child != null) {
       assert(child.parentData is StackParentData);
@@ skipping 40 matching lines @@
   }
 
   void hitTestChildren(HitTestResult result, { Point position }) {
     defaultHitTestChildren(result, position: position);
   }
 
   void paint(RenderCanvas canvas) {
     defaultPaint(canvas);
   }
 }