Fixing Node.nodes.first.

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 9e734b8053de22a76cc226361806fee536a53b6a..4e8149b3276f24f18287948ac435541ad998752b 100644
--- a/sdk/lib/html/dart2js/html_dart2js.dart
+++ b/sdk/lib/html/dart2js/html_dart2js.dart
@@ -17400,12 +17400,12 @@ class _ChildNodeListLazy implements List {
 
 
   Node get first {
-    Node result = JS('Node', '#.firstChild', _this);
+    Node result = JS('Node|Null', '#.firstChild', _this);
     if (result == null) throw new StateError("No elements");
     return result;
   }
   Node get last {
-    Node result = JS('Node', '#.lastChild', _this);
+    Node result = JS('Node|Null', '#.lastChild', _this);
     if (result == null) throw new StateError("No elements");
     return result;
   }
@@ -17413,7 +17413,7 @@ class _ChildNodeListLazy implements List {
     int l = this.length;
     if (l == 0) throw new StateError("No elements");
     if (l > 1) throw new StateError("More than one element");
-    return JS('Node', '#.firstChild', _this);
+    return JS('Node|Null', '#.firstChild', _this);
   }
 
   Node min([int compare(Node a, Node b)]) {