Add List.first.

sdk/lib/html/templates/html/impl/impl_Element.darttemplate

Index: sdk/lib/html/templates/html/impl/impl_Element.darttemplate
diff --git a/sdk/lib/html/templates/html/impl/impl_Element.darttemplate b/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
index d01680db57a0686652d1577c32c4b177eb297bb5..bfe269eaf0cdbd66c352e64f2d6ead3a4396d4fa 100644
--- a/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
+++ b/sdk/lib/html/templates/html/impl/impl_Element.darttemplate
@@ -145,6 +145,11 @@ class _ChildrenElementList implements List {
     return result;
   }
 
+  Element get first {
+    return _element.$dom_firstElementChild;
+  }
+
+
   Element get last {
     return _element.$dom_lastElementChild;
   }
@@ -159,10 +164,6 @@ class _FrozenElementList implements List {
 
   _FrozenElementList._wrap(this._nodeList);
 
-  Element get first {
-    return _nodeList[0];
-  }
-
   bool contains(Element element) {
     for (Element el in this) {
       if (el == element) return true;
@@ -271,6 +272,8 @@ class _FrozenElementList implements List {
     throw new UnsupportedError('');
   }
 
+  Element get first => _nodeList.first;
+
   Element get last => _nodeList.last;
 }