There are a bunch of conversion functions between Qt and WebCore types at the top of GraphicsContext.cpp All cases should be handled in all functions, instead of having a qWarning() and returning some arbitrary "sane default". Also, Qt::MiterJoin shouldn't be used anywhere (it's currently impossibly returned by toQtLineJoin().)
Created attachment 74755 [details] Patch
Comment on attachment 74755 [details] Patch LGTM
Landed in <http://trac.webkit.org/changeset/72668>