Function fetch_a_single_module_script 

pub(crate) fn fetch_a_single_module_script(
    url: ServoUrl,
    owner: ModuleOwner,
    destination: Destination,
    options: ScriptFetchOptions,
    referrer: Referrer,
    module_type: Option<ModuleType>,
    is_top_level: bool,
    introduction_type: Option<&'static CStr>,
    on_complete: impl FnOnce(Option<Rc<ModuleTree>>) + 'static,
)

https://html.spec.whatwg.org/multipage/#fetch-a-single-module-script