Add the floating action button to stocks2

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

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import '../fn2.dart';
 import 'dart:sky' as sky;
 import '../rendering/box.dart';
 import '../rendering/object.dart';
 
 
@@ skipping 99 matching lines @@
       body.parentData.position = new sky.Point(0.0, bodyPosition);
     }
     if (_slots[ScaffoldSlots.drawer] != null) {
       RenderBox drawer = _slots[ScaffoldSlots.drawer];
       drawer.layout(new BoxConstraints(minWidth: 0.0, maxWidth: size.width, minHeight: size.height, maxHeight: size.height));
       assert(drawer.parentData is BoxParentData);
       drawer.parentData.position = new sky.Point(0.0, 0.0);
     }
     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();
     }
   }
 
   void paint(RenderObjectDisplayList canvas) {
     for (ScaffoldSlots slot in [ScaffoldSlots.body, ScaffoldSlots.statusBar, ScaffoldSlots.toolbar, ScaffoldSlots.floatingActionButton, ScaffoldSlots.drawer]) {
       RenderBox box = _slots[slot];
       if (box != null) {
         assert(box.parentData is BoxParentData);
         canvas.paintChild(box, box.parentData.position);
       }
@@ skipping 71 matching lines @@
   void syncRenderObject(UINode old) {
     super.syncRenderObject(old);
     syncChild(toolbar, old is Scaffold ? old.toolbar : null, ScaffoldSlots.toolbar);
     syncChild(body, old is Scaffold ? old.body : null, ScaffoldSlots.body);
     syncChild(statusbar, old is Scaffold ? old.statusbar : null, ScaffoldSlots.statusBar);
     syncChild(drawer, old is Scaffold ? old.drawer : null, ScaffoldSlots.drawer);
     syncChild(floatingActionButton, old is Scaffold ? old.floatingActionButton : null, ScaffoldSlots.floatingActionButton);
   }
 
 }