Chrome roll.

tools/dom/scripts/idlparser.py

 #!/usr/bin/python
 # Copyright (c) 2011, 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.
 
 import re
 import subprocess
 import tempfile
 
 from pegparser import *
@@ skipping 216 matching lines @@
     # Operation arguments:
     def _Arguments():
       return MAYBE(MANY(Argument, ','))
 
     def Argument():
       return syntax_switch(
         # Web IDL:
         [MAYBE(ExtAttrs), MAYBE(Optional), MAYBE('in'),
          MAYBE(Optional), Type, MAYBE(AnEllipsis), Id],
         # WebKit:
+        # TODO(antonm): cleanup this mess.
         [MAYBE(Optional), MAYBE('in'), MAYBE(Optional),
-         MAYBE(ExtAttrs), Type, Id])
+         MAYBE(ExtAttrs), MAYBE(Optional), Type, Id])
 
     def Optional():
       return 'optional'
 
     def AnEllipsis():
       return '...'
 
     # Exceptions (Web IDL).
     def ExceptionDef():
       return ['exception', Id, '{', MAYBE(MANY(_ExceptionMember)), '}',
@@ skipping 162 matching lines @@
     Args:
       content -- text to parse.
       defines -- an array of pre-processor defines.
       includePaths -- an array of path strings used by the
         gcc pre-processor.
     """
     if self._syntax == WEBKIT_SYNTAX:
       content = self._pre_process(content, defines, includePaths)
 
     return self._pegparser.parse(content)