r65681 caused the caret to use the last-computed caret rect when painting, rather than forcing a style update. That seems to have changed the drawing of the caret in the middle of editing. This testcase shows a pixel difference as a result:
Hmm, this only seems to be when you hit the end of the field and start to scroll.
Created attachment 64995 [details]
This looks good to me.
http://trac.webkit.org/changeset/65934 might have broken Leopard Intel Release (Tests)
The following changes are on the blame list: