Function finish_fetching_a_classic_script 

fn finish_fetching_a_classic_script(
    elem: &HTMLScriptElement,
    script_kind: ExternalScriptKind,
    url: ServoUrl,
    load: Result<Script, ()>,
    cx: &mut JSContext,
)

Final steps of https://html.spec.whatwg.org/multipage/#prepare-the-script-element