Use new delegate for NSScrollerImp to give an NSAppearance to use for async scrollbars.
<rdar://problem/41225839>
Created attachment 353138 [details] Patch
Created attachment 353151 [details] Patch
Comment on attachment 353151 [details] Patch Clearing flags on attachment: 353151 Committed r237466: <https://trac.webkit.org/changeset/237466>
All reviewed patches have been landed. Closing bug.
*** Bug 191140 has been marked as a duplicate of this bug. ***