Test for http://bugzilla.opendarwin.org/show_bug.cgi?id=6431 REGRESSION: style change where :hover changes only an :after style doesn't work.

The line at the top of the page should read “This is a test and generated content” or “This is a test and generated hover content” depending on whether it is hovered.

To reproduce the bug outside of DumpRenderTree, mouse over the div several times, and the style change won't update every time like it should.