IDL: Add IdlTypeBase.is_traceable

Source/bindings/scripts/v8_union.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import v8_utilities
 
 
 UNION_H_INCLUDES = frozenset([
     'bindings/core/v8/ExceptionState.h',
     'bindings/core/v8/V8Binding.h',
@@ skipping 66 matching lines @@
     if interface_info:
         cpp_includes.update(interface_info.get('dependencies_include_paths', []))
         header_forward_decls.add(member.name)
     return {
         'cpp_name': v8_utilities.uncapitalize(member.name),
         'cpp_type': member.cpp_type_args(used_in_cpp_sequence=True),
         'cpp_local_type': member.cpp_type,
         'cpp_value_to_v8_value': member.cpp_value_to_v8_value(
             cpp_value='impl.getAs%s()' % member.name, isolate='isolate',
             creation_context='creationContext'),
-        'is_traceable': (member.is_garbage_collected or
-                         member.is_will_be_garbage_collected),
+        'is_traceable': member.is_traceable,
         'rvalue_cpp_type': member.cpp_type_args(used_as_rvalue_type=True),
         'specific_type_enum': 'SpecificType' + member.name,
         'type_name': member.name,
         'v8_value_to_local_cpp_value': member.v8_value_to_local_cpp_value(
             {}, 'v8Value', 'cppValue', needs_exception_state_for_string=True),
     }