Make OptionElement construtor arguments named optional parameters.

tools/dom/scripts/generator.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 provides shared functionality for systems to generate
 Dart APIs from the IDL database."""
 
 import copy
 import json
 import monitored
 import os
 import re
-from htmlrenamer import html_interface_renames, typed_array_renames
+from htmlrenamer import custom_html_constructors, html_interface_renames, \
+    typed_array_renames
 
 _pure_interfaces = monitored.Set('generator._pure_interfaces', [
     # TODO(sra): DOMStringMap should be a class implementing Map<String,String>.
     'DOMStringMap',
     'ChildNode',
     'EventListener',
     'MediaQueryListListener',
     'MutationCallback',
     'NavigatorID',
     'NavigatorOnLine',
@@ skipping 281 matching lines @@
     idl_args = [func_value.arguments]
     name = func_value.id
   else:
     return None
 
   info = OperationInfo()
   info.overloads = None
   info.idl_args = idl_args
   info.declared_name = name
   info.name = name
-  info.constructor_name = None
+  info.constructor_name = ('_' if interface.id in custom_html_constructors
+      else None)
   info.js_name = name
   info.type_name = interface.id
   info.param_infos = _BuildArguments(idl_args, interface, constructor=True)
   info.requires_named_arguments = False
   info.pure_dart_constructor = False
   return info
 
 def IsDartListType(type):
   return type == 'List' or type.startswith('sequence<')
 
@@ skipping 912 matching lines @@
     if type_data.clazz == 'BasicTypedList':
       if type_name == 'ArrayBuffer':
         dart_interface_name = 'ByteBuffer'
       else:
         dart_interface_name = self._renamer.RenameInterfaceId(type_name)
       return BasicTypedListIDLTypeInfo(
           type_name, type_data, dart_interface_name, self)
 
     class_name = '%sIDLTypeInfo' % type_data.clazz
     return globals()[class_name](type_name, type_data)