This is related to bug 52556. Pattern fillStyle has the same issue.
Created attachment 79140 [details] Patch
Created attachment 79141 [details] Patch
Comment on attachment 79141 [details] Patch LGTM!
Comment on attachment 79141 [details] Patch Clearing flags on attachment: 79141 Committed r75973: <http://trac.webkit.org/changeset/75973>
All reviewed patches have been landed. Closing bug.