This breaks the ability to drop multiple attachment elements into Mail, and also breaks attachment progress rendering in Mail.
Created attachment 331975 [details] Patch
<rdar://problem/36431678>
Comment on attachment 331975 [details] Patch Thanks for the review!
Comment on attachment 331975 [details] Patch Clearing flags on attachment: 331975 Committed r227371: <https://trac.webkit.org/changeset/227371>
All reviewed patches have been landed. Closing bug.