Fixing dart2js compilation warning.

sdk/lib/html/dart2js/html_dart2js.dart

Index: sdk/lib/html/dart2js/html_dart2js.dart
diff --git a/sdk/lib/html/dart2js/html_dart2js.dart b/sdk/lib/html/dart2js/html_dart2js.dart
index 6960ebbd7aae4233a52ee496c242b33fe6e1a3d1..0709df24bee3cd3abcc909ee7a948b4886c83e85 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -15828,14 +15828,15 @@ class Node extends EventTarget native "Node" {
    */
   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) {