We are seeing frame drops during Flash media playback due to sandbox violations. Some IOKit properties are being blocked, preventing efficient decode logic from being used.
This was likely introduced in Bug 169331.
Created attachment 330393 [details] Patch
<rdar://problem/34843448>
Comment on attachment 330393 [details] Patch Clearing flags on attachment: 330393 Committed r226369: <https://trac.webkit.org/changeset/226369>
All reviewed patches have been landed. Closing bug.