Position the popup menu in stocks2 correctly

sky/sdk/lib/framework/fn2.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.
 
 library fn;
 
 import 'app.dart';
 import 'dart:async';
 import 'dart:collection';
 import 'dart:mirrors';
@@ skipping 686 matching lines @@
 }
 
 class StackContainer extends MultiChildRenderObjectWrapper {
   RenderStack root;
   RenderStack createNode() => new RenderStack();
 
   StackContainer({ Object key, List<UINode> children })
     : super(key: key, children: children);
 }
 
+class StackPositionedChild extends ParentDataNode {
+  StackPositionedChild(UINode content, {
+    double top, double right, double bottom, double left
+  }) : super(content, new StackParentData()..top = top
+                                           ..right = right
+                                           ..bottom = bottom
+                                           ..left = left);
+}
+
 class Paragraph extends RenderObjectWrapper {
   RenderParagraph root;
   RenderParagraph createNode() => new RenderParagraph(text: text);
 
   final String text;
 
   Paragraph({ Object key, this.text }) : super(key: key);
 
   void syncRenderObject(UINode old) {
     super.syncRenderObject(old);
@@ skipping 334 matching lines @@
     assert(root.parent is RenderView);
   }
 }
 
 class Text extends Component {
   Text(this.data) : super(key: '*text*');
   final String data;
   bool get interchangeable => true;
   UINode build() => new Paragraph(text: data);
 }