Turn on constructible & adoptable CSSStyleSheet objects, now that it is fully implemented.
Pull request: https://github.com/WebKit/WebKit/pull/4903
Committed 255067@main (5de6ac49fed8): <https://commits.webkit.org/255067@main> Reviewed commits have been landed. Closing PR #4903 and removing active labels.
<rdar://problem/100661285>