Open the attached html file and look at the result of the layout. The layout seems incorrect and when it is compared with FireFox, FireFox seems to do a better layout than WebKit. I think neither of FireFox nor WebKit is working 100% correct with this test file. But in WebKit, the text is truncated and the borders around the page elements are drawn correctly. See attached images.
Created attachment 240578 [details] Test file for nested css column properties
Created attachment 240579 [details] WebKit display for nested css column properties
Created attachment 240580 [details] FireFox display for nested css column properties
Created attachment 240581 [details] Another test for nested css column properties