GraphicsLayerCA only updates media element layers on the main thread to avoid problems is low level frameworks. This is not necessary when using AVFoundation directly.
Created attachment 222705 [details] Proposed patch
Comment on attachment 222705 [details] Proposed patch Clearing flags on attachment: 222705 Committed r163104: <http://trac.webkit.org/changeset/163104>
All reviewed patches have been landed. Closing bug.