The images are the problem. If you place your mouse on them, so they stop scrolling, CPU usage goes back to 0%. I think it's a layout problem (and a known one).
If you search Core:Layout for anything related to CPU and scrolling images quite a few come back. It would take a while to figure out which to count as the main bugs and which are duplicates so I'll go ahead and add this to the bunch.
Related bug: probably 693105.