Add test coverage.
Created attachment 376727 [details] WIP
Created attachment 376802 [details] Patch
Created attachment 376809 [details] Patch
Created attachment 376813 [details] Patch
Comment on attachment 376813 [details] Patch r=me
Comment on attachment 376813 [details] Patch Clearing flags on attachment: 376813 Committed r248947: <https://trac.webkit.org/changeset/248947>
All reviewed patches have been landed. Closing bug.
<rdar://problem/54560821>