Trait CustomElementRegistryMethods 
Source pub trait CustomElementRegistryMethods<D>{
    // Required methods
    fn Define(
        &self,
        name: DOMString,
        constructor_: Rc<CustomElementConstructor<D>>,
        options: &ElementDefinitionOptions,
        _can_gc: CanGc,
    ) -> Result<(), Error>;
    fn Get(
        &self,
        cx: JSContext,
        name: DOMString,
        rval: MutableHandle<'_, Value>,
    );
    fn GetName(
        &self,
        constructor: Rc<CustomElementConstructor<D>>,
    ) -> Option<DOMString>;
    fn WhenDefined(
        &self,
        name: DOMString,
        _comp: InRealm<'_>,
        _can_gc: CanGc,
    ) -> Rc<<D as DomTypes>::Promise>;
    fn Upgrade(&self, root: &<D as DomTypes>::Node);
}