Fixing dart2js compilation warning.

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 0ba289f732d149552bd51c2014d5e71c469ca4ca..ebf1be96c6f16909e1e6afd4397d670203a40e9e 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -16873,14 +16873,15 @@ class Node extends EventTarget {
    */
   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) {