Spelling error dots drawn in wrong place for overlapping lines.
Created attachment 324471 [details]
[Screenshot] Expected (shipping Safari on macOS Sierra)
Disregarding the orientation of the dots (this was fixed in bug #176949), this screenshot represents the expected position for the dots.
Created attachment 324472 [details]
Screenshot following r223699.
Created attachment 324473 [details]
Created attachment 324477 [details]
Patch and layout tests
As it turns outs I decided to revert r223699 in <https://trac.webkit.org/changeset/223840> because it causes regressions in addition to the one reported in this bug. I will incorporate the source code changes from the patch on this bug (attachment #324477 [details]) into an updated patch for bug #178232. I am re-purposing this bug to land the layout tests included in attachment #324477 [details]. This will ensure that we do not regress painting of spelling dots in overlapping lines.
Committed r223842: <https://trac.webkit.org/changeset/223842>