MAP_CACHE_INDEX   154 src/contexts.h   V(MAP_CACHE_INDEX, Object, map_cache) \
MAP_CACHE_INDEX  2477 src/mark-compact.cc           HeapObject::cast(context->get(Context::MAP_CACHE_INDEX));
MAP_CACHE_INDEX  2504 src/mark-compact.cc           context->set(Context::MAP_CACHE_INDEX, heap()->undefined_value());