Why is JQuery slower on Chrome 10 than on Chrome 8?

According to the JQuery 1.5 release notes, the speed performance charts show that Chrome 8 is faster for the mentioned JQuery methods children(), prev(), next().

I wonder how that would be, since recently Chrome reported they are using the new crankshaft javascript optimization engine

Screenshot where you can see the Chrome 8 columns are taller than Chrome 10 (and thus faster):

So the question is: If the numbers reported here is true, then why w开发者_StackOverflowould Chrome 10 be a slower browser than the mainstream Chrome 8?

Because Chrome 10 is still beta?

Is the next version of any software ever faster than it's predecessor?

Unless a release involves a major refactoring or redesign, it's probably got the same engine with more stuff hanging off it. That means slower.