This is an unexpected change of bug 34758. Bug 34758 made us abide by percent width when there are only percent columns on a colspan. The bug is simple and stems from the fact that we are setting the min / max effective column width but forget to update the cell's min / max (remaining) logical width like the rest of the code. Patch and test case to follow shortly.
Created attachment 137735 [details] Propsed patch 1: Account for allocated min / max cell's logical width.
Comment on attachment 137735 [details] Propsed patch 1: Account for allocated min / max cell's logical width. Clearing flags on attachment: 137735 Committed r114574: <http://trac.webkit.org/changeset/114574>
All reviewed patches have been landed. Closing bug.