It seems the test started to fail since r242308 (Finish removing String::format https://bugs.webkit.org/show_bug.cgi?id=194893)
The test is actually flaky. First Crash happened in r239157 ([FreeType] Remove HarfBuzzFace https://bugs.webkit.org/show_bug.cgi?id=192589).
The test(s) filed under this bug have been consistently passing for the last 4000 revisions. Marking bug as fixed. Committed r263254: <https://trac.webkit.org/changeset/263254>
<rdar://problem/64520270>