Function cross_origin_get 

pub(crate) fn cross_origin_get<D: DomTypes>(
    cx: &mut CurrentRealm<'_>,
    proxy: HandleObject<'_>,
    receiver: HandleValue<'_>,
    id: HandleId<'_>,
    vp: MutableHandleValue<'_>,
) -> bool

Implementation of CrossOriginGet.

cx and proxy are expected to be different-Realm here. proxy is a proxy for a maybe-cross-origin object.