Support Dart optional arguments which are not dispatched, but instead use default values.

client/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 @@
       if not attribute.is_read_only:
         setter_attr = copy.deepcopy(attribute)
         setter_attr.is_fc_setter = True
         new_attributes.append(setter_attr)
     interface.attributes = new_attributes
 
     # Remove optional annotations from legacy optional 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()):
+          argument.is_optional = True
+          argument.ext_attrs['RequiredCppParameter'] = None
+          continue
+
         if argument.is_optional:
           if 'Optional' in argument.ext_attrs:
             optional_value = argument.ext_attrs['Optional']
             if optional_value:
-              if (interface.id, op.id, argument.id) not in optional_argument_whitelist:
-                argument.is_optional = False
-                del argument.ext_attrs['Optional']
+              argument.is_optional = False
+              del argument.ext_attrs['Optional']
 
     # split operations with optional args into multiple operations
     new_ops = []
     for op in interface.operations:
       for i in range(0, len(op.arguments)):
         if op.arguments[i].is_optional:
           op.arguments[i].is_optional = False
           new_op = copy.deepcopy(op)
           new_op.arguments = new_op.arguments[:i]
           new_ops.append(new_op)
@@ skipping 454 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)