Scroll To Text Fragment indicator flash not always apparent.
Pull request: https://github.com/WebKit/WebKit/pull/4269
<rdar://problem/99827988>
rdar://99668762
Committed 254403@main (f017f4f3662e): <https://commits.webkit.org/254403@main> Reviewed commits have been landed. Closing PR #4269 and removing active labels.