Function html_constructor 

fn html_constructor(
    cx: &mut JSContext,
    global: &GlobalScope,
    call_args: &CallArgs,
    check_type: fn(&Element) -> bool,
    proto_id: ID,
    creator: unsafe fn(&mut JSContext, HandleObject<'_>, *mut ProtoOrIfaceArray),
) -> Result<(), ()>

https://html.spec.whatwg.org/multipage/#htmlconstructor