The following test crashes sometimes on GTK: imported/w3c/web-platform-tests/encoding/legacy-mb-korean/euc-kr/euckr-decode-cseuckr.html So far all the crashes have occurred in release, so there is no traceback.
According to wktesthunter, last CRASH was r230391 (April 9 2018). Replaced the CRASH expectation with a Timeout one for the debug bot in bug207714 (and tracked in bug207711).