Vladimir: The drivers are now fixed, and cairo will use XRender for EXTEND_PAD as of commit a1d0a06b[1], provided that a 1.7 X server is running, so it looks like this can be finally fixed in firefox.
[1] http://cgit.freedesktop.org/cairo/commit/?id=a1d0a06b6275cac3974be84919993e187394fe43
Vladimir: The drivers are now fixed, and cairo will use XRender for EXTEND_PAD as of commit a1d0a06b[1], provided that a 1.7 X server is running, so it looks like this can be finally fixed in firefox.
[1] http:// cgit.freedeskto p.org/cairo/ commit/ ?id=a1d0a06b627 5cac3974be84919 993e187394fe43