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

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

 // Copyright (c) 2012, 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.
 
 // WARNING: Do not edit - generated code.
 
 part of $LIBRARYNAME;
 
-$(ANNOTATIONS)$(NATIVESPEC)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
+$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   $if DART2JS
     @Creates('Null')  // Set from Dart code; does not instantiate a native type.
   $endif
   var _dartDetail;
 
   factory $CLASSNAME(String type,
       {bool canBubble: true, bool cancelable: true, Object detail}) {
 
     final CustomEvent e = document._createEvent('CustomEvent');
 
@@ skipping 19 matching lines @@
 
   @DomName('CustomEvent.detail')
   get detail {
     if (_dartDetail != null) {
       return _dartDetail;
     }
     return _detail;
   }
 $!MEMBERS
 }