Split Size into Size and Offset.

sky/examples/game/lib/sprite_box.dart

Index: sky/examples/game/lib/sprite_box.dart
diff --git a/sky/examples/game/lib/sprite_box.dart b/sky/examples/game/lib/sprite_box.dart
index f3020316b9017cf292328d31ddffb5c288acba67..6e9d3453c04c760ef13b1e9704c23deba6dc94b4 100644
--- a/sky/examples/game/lib/sprite_box.dart
+++ b/sky/examples/game/lib/sprite_box.dart
@@ -84,7 +84,7 @@ class SpriteBox extends RenderBox {
   NodeWithSize get rootNode => _rootNode;
 
   void performLayout() {
-    size = constraints.constrain(Size.infinite);
+    size = constraints.biggest;
     _invalidateTransformMatrix();
     _callSpriteBoxPerformedLayout(_rootNode);
   }
@@ -378,4 +378,4 @@ class SpriteBoxEvent {
   ///
   ///     var event = new SpriteBoxEvent(new Point(50.0, 50.0), 'pointerdown', 0);
   SpriteBoxEvent(this.boxPosition, this.type, this.pointer);
-}
+}