Fix the floating action button.

sky/engine/core/painting/Rect.dart

Index: sky/engine/core/painting/Rect.dart
diff --git a/sky/engine/core/painting/Rect.dart b/sky/engine/core/painting/Rect.dart
index ee1eb6a31513ddfff0fd98a43bbb23fb20a2693f..85fe07331e05b24ac4583377b91de6b21ba90b5b 100644
--- a/sky/engine/core/painting/Rect.dart
+++ b/sky/engine/core/painting/Rect.dart
@@ -30,14 +30,23 @@ class Rect {
   double get right => _value[2];
   double get bottom => _value[3];
 
-  Point get center => new Point(left + right / 2.0, top + bottom / 2.0);
+  double get width => right - left;
+  double get height => bottom - top;
+
+  Size get size => new Size(width, height);
+
+  double get shortestSide {
+    double w = width.abs();
+    double h = height.abs();
+    return w < h ? w : h;
+  }
+
+  Point get center => new Point(left + width / 2.0, top + height / 2.0);
   Point get topLeft => new Point(left, top);
   Point get topRight => new Point(right, top);
   Point get bottomLeft => new Point(left, bottom);
   Point get bottomRight => new Point(right, bottom);
 
-  Size get size => new Size(right - left, bottom - top);
-
   // Rects are inclusive of the top and left edges but exclusive of the bottom
   // right edges.
   bool contains(Point point) {