Implement v8-like overload resolving.

lib/dom/scripts/databasebuilder.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 copy
 import database
 import idlparser
 import logging
 import os
@@ skipping 108 matching lines @@
         setter_attr = copy.deepcopy(attribute)
         setter_attr.is_fc_setter = True
         new_attributes.append(setter_attr)
     interface.attributes = new_attributes
 
     # Add 'Optional' attribute to whitelisted arguments.
     for op in interface.operations:
       for i in range(0, len(op.arguments)):
         argument = op.arguments[i]
         in_optional_whitelist = (interface.id, op.id, argument.id) in optional_argument_whitelist
-        if in_optional_whitelist or set(['Optional', 'Callback']).issubset(argument.ext_attrs.keys()):
+        if in_optional_whitelist:
           argument.ext_attrs['Optional'] = None
-          argument.ext_attrs['RequiredCppParameter'] = None
 
   def _rename_types(self, idl_file, import_options):
     """Rename interface and type names with names provided in the
     options. Also clears scopes from scoped names"""
 
     def rename(name):
       name_parts = name.split('::')
       name = name_parts[-1]
       if name in import_options.type_rename_map:
         name = import_options.type_rename_map[name]
@@ skipping 414 matching lines @@
             annotation = idl_node.annotations[source]
             for name, value in annotation.items():
               if (name in top_level_annotation
                   and value == top_level_annotation[name]):
                 del annotation[name]
 
         map(normalize, interface.parents)
         map(normalize, interface.constants)
         map(normalize, interface.attributes)
         map(normalize, interface.operations)