Rework overloads/optionals dispatch to use new ?a syntax.

lib/html/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 re
@@ skipping 339 matching lines @@
     type_name: A string, the name of the return type of the operation.
     param_infos: A list of ParamInfo.
   """
 
   def ParametersInterfaceDeclaration(self, rename_type):
     """Returns a formatted string declaring the parameters for the interface."""
     return self._FormatParams(
         self.param_infos, None,
         lambda param: TypeOrNothing(rename_type(param.dart_type), param.type_id))
 
-  def ParametersImplementationDeclaration(
-      self, rename_type, default_value='null'):
+  def ParametersImplementationDeclaration(self, rename_type):
     """Returns a formatted string declaring the parameters for the
     implementation.
 
     Args:
       rename_type: A function that allows the types to be renamed.
         The function is applied to the parameter's dart_type.
     """
     return self._FormatParams(
-        self.param_infos, default_value,
+        self.param_infos, 'null',
         lambda param: TypeOrNothing(rename_type(param.dart_type)))
 
   def ParametersAsArgumentList(self):
     """Returns a string of the parameter names suitable for passing the
     parameters as arguments.
     """
     return ', '.join(map(lambda param_info: param_info.name, self.param_infos))
 
   def _FormatParams(self, params, default_value, type_fn):
     def FormatParam(param):
@@ skipping 488 matching lines @@
     if match:
       if type_name == 'DOMString[]':
         return DOMStringArrayTypeInfo(TypeData('Sequence'), self.TypeInfo('DOMString'))
       item_info = self.TypeInfo(match.group(1) or match.group(2))
       return SequenceIDLTypeInfo(type_name, TypeData('Sequence'), item_info)
     if not type_name in _idl_type_registry:
       return InterfaceIDLTypeInfo(type_name, TypeData('Interface'))
     type_data = _idl_type_registry.get(type_name)
     class_name = '%sIDLTypeInfo' % type_data.clazz
     return globals()[class_name](type_name, type_data)