To reproduce, open the URL. There should be 20px of extra spacing between the words, but after <http://trac.webkit.org/r125578>, there is no extra spacing. This differs from Firefox 15.0.1.
The same thing happens with horizontal tabs.
Created attachment 164294 [details]
Apply word spacing to all characters that are treated as space
Fixed in <http://trac.webkit.org/r128692>.