I don't understand the implementation of CustomProtocolManagerImpl::registerScheme. * It calls g_type_class_ref twice for no apparent reason, and with no paired calls to g_type_class_unref that I could find. The second use should probably be g_type_class_peek instead. Maybe the first use should be paired with a g_type_class_unref somewhere. Even if we don't care about leaking the class struct, I don't see why we should ref it twice in the same place. * It assigns |this| to the |client| member of WebKitSoupRequestGenericClass, but that means it will clobber any other CustomProtocolManagerImpls that have previously registered themselves with the WebKitSoupRequestGenericClass struct. I guess only a single CustomProtocolManagerImpl is ever intended to be created, but it's not a singleton, so it feels kinda fragile.