Fixing dart2js compilation warning.

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
 import 'dart:json' as json;
@@ skipping 15810 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 13497 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }