The specificity of :host in WebKit does not match that of Chrome & Firefox. <rdar://problem/51963736>
Created attachment 380105 [details] test case
<rdar://problem/66292568>
Created attachment 406780 [details] patch
Committed r265812: <https://trac.webkit.org/changeset/265812> All reviewed patches have been landed. Closing bug and clearing flags on attachment 406780 [details].