In order to fix the bug 166748, we need to be able to tell whether a given node is a ShadowRoot or not fast.
Created attachment 349105 [details] Cleanup
Created attachment 349107 [details] Patch for landing
Comment on attachment 349107 [details] Patch for landing Wait for EWS
Committed r235780: <https://trac.webkit.org/changeset/235780>
<rdar://problem/44212947>