Teach stack to size to the max of its non-positioned children

sky/sdk/lib/framework/rendering/box.dart

Index: sky/sdk/lib/framework/rendering/box.dart
diff --git a/sky/sdk/lib/framework/rendering/box.dart b/sky/sdk/lib/framework/rendering/box.dart
index f6bf0da0977043b5f84b285908bdd0ee37d90250..4b8a3a7a2837327bc35ee332c689d7a6c36db406 100644
--- a/sky/sdk/lib/framework/rendering/box.dart
+++ b/sky/sdk/lib/framework/rendering/box.dart
@@ -402,6 +402,9 @@ class RenderShrinkWrapWidth extends RenderProxyBox {
 
   BoxConstraints _getInnerConstraints(BoxConstraints constraints) {
     double width = child.getMaxIntrinsicWidth(constraints);
+    if (width != constraints.constrainWidth(width)) {
+      print ("$width $constraints");
+    }
     assert(width == constraints.constrainWidth(width));
     return constraints.applyWidth(width);
   }