Clean up a bunch of our Dart code.

sky/engine/core/painting/Size.dart

Index: sky/engine/core/painting/Size.dart
diff --git a/sky/engine/core/painting/Size.dart b/sky/engine/core/painting/Size.dart
index b4a1e9fe3c3c3db57e1e9feb1b2bb68eec95299f..ed02a664f919c2564764ca5c52a2105bfc83c89d 100644
--- a/sky/engine/core/painting/Size.dart
+++ b/sky/engine/core/painting/Size.dart
@@ -7,14 +7,13 @@ part of dart.sky;
 /// Holds a 2D floating-point size.
 /// Think of this as a vector from Point(0,0) to Point(size.width, size.height)
 class Size {
-  final double width;
-  final double height;
-
   const Size(this.width, this.height);
-
   const Size.fromWidth(this.width) : height = double.INFINITY;
   const Size.fromHeight(this.height) : width = double.INFINITY;
 
+  final double width;
+  final double height;
+
   static const Size zero = const Size(0.0, 0.0);
   static const Size infinite = const Size(double.INFINITY, double.INFINITY);