Fix dartium checked mode build break.

client/dom/templates/html/impl/impl_Node.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   _NodeListImpl get nodes() {
     final list = _childNodes;
     list._parent = this;
     return list;
   }
 
   void set nodes(Collection<Node> value) {
     // Copy list first since we don't want liveness during iteration.
     // TODO(jacobr): there is a better way to do this.
+    List copy = new List.from(value);
     text = '';
-    for (Node node in value) {
+    for (Node node in copy) {
       _appendChild(node);
     }
   }
 
   // TODO(jacobr): should we throw an exception if parent is already null?
   _NodeImpl remove() {
     if (this.parent != null) {
       this.parent._removeChild(this);
     }
     return this;
   }
 
   _NodeImpl replaceWith(Node otherNode) {
     try {
       this.parent._replaceChild(otherNode, this);
     } catch(var e) {
       
     };
     return this;
   }
 
 $!MEMBERS
 }