assignedSlot property should be on Text, not CharacterData as per: https://dom.spec.whatwg.org/#mixin-slotable
<rdar://problem/27201687>
Created attachment 282926 [details] Patch
Created attachment 282934 [details] Patch
Comment on attachment 282934 [details] Patch Clearing flags on attachment: 282934 Committed r202873: <http://trac.webkit.org/changeset/202873>
All reviewed patches have been landed. Closing bug.