Fix bogus asserts in searchForOldNode

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 555 matching lines @@
       if (currentNode.interchangeable)
         return false; // never re-order these nodes
 
       ensureOldIdMap();
       oldNode = oldNodeIdMap[currentNode._key];
       if (oldNode == null)
         return false;
 
       oldNodeIdMap[currentNode._key] = null; // mark it reordered
       assert(root is ContainerRenderObjectMixin);
-      assert(oldNode.root is ContainerRenderObjectMixin);
+      assert(old.root is ContainerRenderObjectMixin);
+      assert(oldNode.root != null);
 
       old.root.remove(oldNode.root);
       root.add(oldNode.root, before: nextSibling);
 
       return true;
     }
 
     // Scan forwards, this time we may re-order;
     nextSibling = root.firstChild;
     while (startIndex < endIndex && oldStartIndex < oldEndIndex) {
@@ skipping 397 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);
 }