mark_old_changes_as_obsolete should return only the changes which were markes obsolete.
Pull request: https://github.com/WebKit/WebKit/pull/3812
Committed 253949@main (0a575f89b84e): <https://commits.webkit.org/253949@main> Reviewed commits have been landed. Closing PR #3812 and removing active labels.
<rdar://problem/99336414>