Via https://bugs.webkit.org/show_bug.cgi?id=147109#c10
.CodeMirror pre { line-height: inherit; } Computed line-height for ".CodeMirror pre" has changed from 11px to 13px. Our new jump to definition feature isn't helpful here — it just highlights "line-height: inherit;".
https://github.com/WebKit/webkit/commit/860334772804d47022a6cbdafd633449fb0d124c#diff-e529b55c5da3924f8dedf9a33ba0708bL112 .CodeMirror { - line-height: 1; This caused the change in the line-height from 11 to 13px.
Created attachment 258883 [details] Patch
Comment on attachment 258883 [details] Patch Clearing flags on attachment: 258883 Committed r188382: <http://trac.webkit.org/changeset/188382>
All reviewed patches have been landed. Closing bug.