Add the floating action button to stocks2

sky/sdk/lib/framework/components2/scaffold.dart

Index: sky/sdk/lib/framework/components2/scaffold.dart
diff --git a/sky/sdk/lib/framework/components2/scaffold.dart b/sky/sdk/lib/framework/components2/scaffold.dart
index e5c6c7d0f633df155b6c378b7678907579b135c4..9b3dbefb3043b403f06628c3239111899662ef97 100644
--- a/sky/sdk/lib/framework/components2/scaffold.dart
+++ b/sky/sdk/lib/framework/components2/scaffold.dart
@@ -117,9 +117,10 @@ class RenderScaffold extends RenderBox {
     }
     if (_slots[ScaffoldSlots.floatingActionButton] != null) {
       RenderBox floatingActionButton = _slots[ScaffoldSlots.floatingActionButton];
-      floatingActionButton.layout(new BoxConstraints(minWidth: 0.0, maxWidth: size.width, minHeight: size.height, maxHeight: size.height));
+      sky.Size area = new sky.Size(size.width + kButtonX, size.height + kButtonY);
+      floatingActionButton.layout(new BoxConstraints.loose(area));
       assert(floatingActionButton.parentData is BoxParentData);
-      floatingActionButton.parentData.position = new sky.Point(size.width - kButtonX, bodyPosition + bodyHeight - kButtonY);
+      floatingActionButton.parentData.position = (area - floatingActionButton.size).toPoint();
     }
   }