Comment 15 for bug 788102

The changes I mentioned in comment #0 were made in other bugs.

I tested scrolling in GMail's conversation view and folder view. During continuous scrolling, at each step we're only painting the scrollbar and the horizontal strip that was scrolled into view. This is good. It's still true even when a chat pane is open --- the chat pane is placed in its own layer, so doesn't cause extra repainting. Everything is working as designed there.

This bookmarklet:
javascript:void((function(){var%20i=0;var%20start=Date.now();function%20f(){if(++i==50){alert((Date.now()-start)+"ms");return;}document.getElementsByTagName('iframe')[4].contentWindow.scrollTo(0,i*5);setTimeout(f,10);}f();})())
is a good way of measuring GMail scrolling performance.

In a big folder view (100 threads of my Bugzilla folder), I get about 2900ms (Linux, megafast PC) without GPU acceleration. That's about 58ms per frame which is definitely not good. (With GL acceleration it's a little slower, which is probably expected on this testcase, since on this machine the X server is perfectly capable of keeping up as it composites everything asynchronously.)