Fixing dart2js compilation warning.

tools/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.
 
 part of $LIBRARYNAME;
 
 /**
  * Lazy implementation of the child nodes of an element that does not request
  * the actual child nodes of an element until strictly necessary greatly
  * improving performance for the typical cases where it is not required.
@@ skipping 212 matching lines @@
 
   /**
    * Inserts all of the nodes into this node directly before refChild.
    *
    * See also:
    *
    * * [insertBefore]
    */
   Node insertAllBefore(Iterable<Node> newNodes, Node refChild) {
     if (newNodes is _ChildNodeListLazy) {
-      if (identical(newNodes._this, this)) {
+      _ChildNodeListLazy otherList = newNodes;
+      if (identical(otherList._this, this)) {
         throw new ArgumentError(newNodes);
       }
 
       // Optimized route for copying between nodes.
-      for (var i = 0, len = newNodes.length; i < len; ++i) {
+      for (var i = 0, len = otherList.length; i < len; ++i) {
         // Should use $dom_firstChild, Bug 8886.
-        this.insertBefore(newNodes[0], refChild);
+        this.insertBefore(otherList[0], refChild);
       }
     } else {
       for (var node in newNodes) {
         this.insertBefore(node, refChild);
       }
     }
   }
 
   /**
    * Print out a String representation of this Node.
@@ skipping 22 matching lines @@
   TemplateInstance _templateInstance;
 
   /** Gets the template instance that instantiated this node, if any. */
   @Experimental
   TemplateInstance get templateInstance =>
       _templateInstance != null ? _templateInstance :
       (parent != null ? parent.templateInstance : null);
 
 $!MEMBERS
 }