pub unsafe extern "C" fn GetSavedFrameAsyncParent(
    cx: *mut JSContext,
    principals: *mut JSPrincipals,
    savedFrame: Handle<*mut JSObject>,
    asyncParentp: MutableHandle<*mut JSObject>,
    selfHosted: SavedFrameSelfHosted,
) -> SavedFrameResultExpand description
Given a SavedFrame JSObject, get its asyncParent SavedFrame object or nullptr
if there is no asyncParent. The asyncParentp out parameter is NOT
guaranteed to be in the cx’s compartment. Defaults to nullptr.