This is related to bug 5255. The shadow color alpha must be multiplied by the context brush alpha.
(In reply to comment #0)
> This is related to bug 5255.
I meant 52559.
Created attachment 79244 [details]
Comment on attachment 79244 [details]
Clearing flags on attachment: 79244
Committed r76033: <http://trac.webkit.org/changeset/76033>
All reviewed patches have been landed. Closing bug.