d4557c4288
This patch implements the sponsor level blocking for the sponsored Top Sites. When a sponsored top site gets dismissed, Firefox will extract the sponsor (hostname) out of the URL, and persist it to the pref `browser.topsites.blockedSponsors` as a JSON array. When Firefox fetches the sponsored tiles from Contile again, it will filter all the tiles whose sponsor has been blocked before. Differential Revision: https://phabricator.services.mozilla.com/D116413