This was happening because I was calling setChanged() from inside updateRendering()
        which causes an infinite loop. I fixed this by deferring the setChanged to the next
        run loop iteration. That made it not infinite loop, but it still retriggers the
        transition forever. The problem is that there is both an 'all' and specific transition
        on 'opacity'. This tickled a bug in AnimationController which causes the opacity 
        transition to get constantly cancelled and then retriggered. The problem is that
        the specific opacity transition has a duration of 0. I got rid of the logic to 
        flush out 0 duration transitions and it is no longer constantly triggered. The
        logic to flush them was just an optimization, and you really need to keep them
        around to make the logic to override earlier animations by later ones work. And there is
        very little overhead in this case anyway, so the optimization was not that useful.

        I made a LayoutTest from the original testcase which tests both the infinite
        loop and constantly triggering animation cases.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@39974 268f45cc-cd09-0410-ab3c-d52691b4dbfc