A text area with a border:0 (as at the Live DOM Viewer) paints the resize drag-corner over the focus ring. Not explicitly stating border corrects the issue. This happens in the Safari 3.0.3 Beta as well as the nightlies, so it is not a regression. Attaching screenshot and test momentarily.
Created attachment 17232 [details] Screenshot showing incorrect painting
Created attachment 17233 [details] Test case with border:0 text area and normal textarea
Looking closer, it seems that the resize corner actually paints over one pixel of the focus ring of a textarea even when no border is explicitly requested.
Created attachment 17234 [details] Zoomed screenshot of unstyled textarea showing one-pixel painting error
Confirmed issue in the latest Webkit.