See the attached test case for examples of blocks not repainting their left overflow when it they (or their content) move. In all cases, pressing the Test button should move "Lorem" together with "ipsum". I am going to attach a patch.
Created attachment 7232 [details] Test case
Created attachment 7233 [details] Include left and top overflow in repaint rects
Comment on attachment 7233 [details] Include left and top overflow in repaint rects Seems to me that overflowRect should be passing the "include interior" boolean along to overflowWidth() and overflowHeight(), no?
Created attachment 7249 [details] Include left and top overflow in repaint rects Corrected the error pointed out by Darin.
Comment on attachment 7249 [details] Include left and top overflow in repaint rects r=me
Eric committed the patch as r13483.
Verified in r13594 nightly.