Switch GA to use clientId instead of userId
Switch GA to use clientId instead of userId

mozilla-services/screenshots,mozilla-services/screenshots,mozilla-services/pageshot,mozilla-services/pageshot,mozilla-services/pageshot,mozilla-services/screenshots,fzzzy/pageshot,fzzzy/pageshot,mozilla-services/screenshots,fzzzy/pageshot,mozilla-services/pageshot,fzzzy/pageshot