Making supressed DOM types abstract

tools/dom/templates/html/dartium/dart_implementation.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;
 
 @DocsEditable
-$(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
+$(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS {
 $!MEMBERS
 }