Revert "Use @Native annotation on dart2js DOM native classes"

tools/dom/templates/html/impl/impl_TreeWalker.darttemplate

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of $LIBRARYNAME;
 
-$(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
+$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   factory TreeWalker(Node root, int whatToShow) {
     return document._createTreeWalker(root, whatToShow, null);
   }
 $!MEMBERS
 }