Simplify counter updates.
<rdar://problem/108189324>
Pull request: https://github.com/WebKit/WebKit/pull/12854
Committed 263127@main (21790649ca10): <https://commits.webkit.org/263127@main> Reviewed commits have been landed. Closing PR #12854 and removing active labels.
Committed 259548.705@safari-7615-branch (2c77ea0857a3): <https://commits.webkit.org/259548.705@safari-7615-branch> Reviewed commits have been landed. Closing PR #570 and removing active labels.