EventTarget was marked as EventTarget upstream.

tools/dom/scripts/dartgenerator.py

 #!/usr/bin/python
 # 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.
 
 """This module generates Dart APIs from the IDL database."""
 
 import emitter
 import idlnode
 import logging
@@ skipping 199 matching lines @@
       for operation in interface.operations:
         if operation.raises:
           exceptions.add(operation.raises.id)
     return exceptions
 
 
   def FixEventTargets(self, database):
     for interface in database.GetInterfaces():
       # Create fake EventTarget parent interface for interfaces that have
       # 'EventTarget' extended attribute.
-      if 'EventTarget' in interface.ext_attrs:
+      if 'EventTarget' in interface.ext_attrs and interface.id != 'EventTarget':
         ast = [('Annotation', [('Id', 'WebKit')]),
                ('InterfaceType', ('ScopedName', 'EventTarget'))]
         interface.parents.append(idlnode.IDLParentInterface(ast))
 
   def AddMissingArguments(self, database):
     ARG = idlnode.IDLArgument([('Type', ('ScopedName', 'object')), ('Id', 'arg')])
     for interface in database.GetInterfaces():
       for operation in interface.operations:
         if operation.ext_attrs.get('CallWith') == 'ScriptArguments|ScriptState':
           operation.arguments.append(ARG)