1276357 - Expose "hasRootDomain" for C++ and JS callers

Status: RESOLVED DUPLICATE of bug 1468503

(Toolkit :: Data Sanitization, defect)

Description

[Lina Butler (ex-Mozilla)]

`hasRootDomain` (https://dxr.mozilla.org/mozilla-central/rev/4d63dde701b47b8661ab7990f197b6b60e543839/toolkit/forgetaboutsite/ForgetAboutSite.jsm#18-41) is currently duplicated in:

* https://dxr.mozilla.org/mozilla-central/rev/4d63dde701b47b8661ab7990f197b6b60e543839/browser/components/sessionstore/Utils.jsm#27-53
* https://dxr.mozilla.org/mozilla-central/rev/4d63dde701b47b8661ab7990f197b6b60e543839/dom/push/PushService.jsm#1212-1237
* https://dxr.mozilla.org/mozilla-central/rev/4d63dde701b47b8661ab7990f197b6b60e543839/dom/workers/ServiceWorkerManager.cpp#2927-2966

It would be good to centralize and expose this somewhere so that C++ and JS code can use it. Martin also suggests using the public suffix list to help determine this, so maybe `nsIEffectiveTLDService` is the right place?