The isStyleRule() checking function should return true for both StyleRule and StyleRuleWithNesting.
<rdar://problem/109254000>
Pull request: https://github.com/WebKit/WebKit/pull/13801
Committed 265028@main (f347660f0196): <https://commits.webkit.org/265028@main> Reviewed commits have been landed. Closing PR #13801 and removing active labels.