One of the subtests fails with Searching for ‘a’ in long string with options [AtWordStarts]: FAIL: Expected a match at 6146,6147 but got a match at 6145,6147 instead. Looks like some sort of text iterator end-of-line handling issue.
Created attachment 387523 [details] patch
https://trac.webkit.org/r254431
<rdar://problem/58529526>