Hmm, unusual. Can you see http://demoseen.com/windowpane/magister.test.html ?
Though interestingly, the behavior in all three Chromes is wildly different: Dev runs 60% CPU use in the rendering process, Beta sometimes uses nothing, sometimes 60%, and Stable uses the same 60% + 120% on "google chrome helper". The alert test works (shows a canvas element) in both Dev and Beta, Stable shows me a "page unresponsive" after a couple seconds and never alerts anything.
Other GL tests work just fine in all 3. I'll be happy to test other things if you can come up with them :)