Ran `arc lint --everything --never-apply-patches --xprofile=profile.json` in rP. Compared the XHProf profile [[https://secure.phabricator.com/xhprof/profile/PHID-FILE-qxksskgu3plnmu5swnki/?symbol=assert_instances_of | before]] and [[https://secure.phabricator.com/xhprof/profile/PHID-FILE-wvx7mf6sxqeti3ajbrle/?symbol=assert_instances_of | after]].