IDL: Add [Custom=CallEpilogue] to eliminate CG special cases

Source/bindings/scripts/v8_methods.py

 # Copyright (C) 2013 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 96 matching lines @@
 
     is_check_security_for_frame = (
         has_extended_attribute_value(interface, 'CheckSecurity', 'Frame') and
         not is_do_not_check_security)
 
     is_check_security_for_window = (
         has_extended_attribute_value(interface, 'CheckSecurity', 'Window') and
         not is_do_not_check_security)
 
     is_raises_exception = 'RaisesException' in extended_attributes
+    is_custom_call_epilogue = has_extended_attribute_value(method, 'Custom', 'CallEpilogue')
 
     return {
         'activity_logging_world_list': v8_utilities.activity_logging_world_list(method),  # [ActivityLogging]
         'arguments': [argument_context(interface, method, argument, index)
                       for index, argument in enumerate(arguments)],
         'argument_declarations_for_private_script':
             argument_declarations_for_private_script(interface, method),
         'conditional_string': v8_utilities.conditional_string(method),
         'cpp_type': (v8_types.cpp_template_type('Nullable', idl_type.cpp_type)
                      if idl_type.is_explicit_nullable else idl_type.cpp_type),
@@ skipping 17 matching lines @@
             any(argument for argument in arguments
                 if (argument.idl_type.name == 'SerializedScriptValue' or
                     argument_conversion_needs_exception_state(method, argument))),
         'idl_type': idl_type.base_type,
         'is_call_with_execution_context': has_extended_attribute_value(method, 'CallWith', 'ExecutionContext'),
         'is_call_with_script_arguments': is_call_with_script_arguments,
         'is_call_with_script_state': is_call_with_script_state,
         'is_check_security_for_frame': is_check_security_for_frame,
         'is_check_security_for_node': is_check_security_for_node,
         'is_check_security_for_window': is_check_security_for_window,
-        'is_custom': 'Custom' in extended_attributes,
+        'is_custom': 'Custom' in extended_attributes and not is_custom_call_epilogue,
+        'is_custom_call_epilogue': is_custom_call_epilogue,
         'is_custom_element_callbacks': is_custom_element_callbacks,
         'is_do_not_check_security': is_do_not_check_security,
         'is_do_not_check_signature': 'DoNotCheckSignature' in extended_attributes,
         'is_explicit_nullable': idl_type.is_explicit_nullable,
         'is_implemented_in_private_script': is_implemented_in_private_script,
         'is_partial_interface_member':
             'PartialInterfaceImplementedAs' in extended_attributes,
         'is_per_world_bindings': 'PerWorldBindings' in extended_attributes,
         'is_raises_exception': is_raises_exception,
         'is_read_only': is_unforgeable(interface, method),
@@ skipping 283 matching lines @@
 
 IdlOperation.returns_promise = property(method_returns_promise)
 
 
 def argument_conversion_needs_exception_state(method, argument):
     idl_type = argument.idl_type
     return (idl_type.v8_conversion_needs_exception_state or
             argument.is_variadic or
             (method.returns_promise and (idl_type.is_string_type or
                                          idl_type.is_enum)))