Earlier quoted context omitted.
Firefox is not slower, it's just that most websites are optimised and tested only or mainly under Chrome. We are slowly getting back to the way things were with IE, but I hope that Mozilla won't give up and switch to blink or webkit like everybody else.
I'm curious as to how you can optimise a site to be faster specifically for Chrome?
1) Write browser-detection code and execute different code, with different performance characteristics, in different browsers. This happens, though less than it used to.
2) Write your code to hit the specific JIT heuristics in a Chrome particularly well, even if that requires contortions that slow it down in every other browser.
3) Write your code to effectively depend on Chrome bugs, where Chrome manages to be faster due to doing something that violates the standards.
4) Arrange the order in which you load your subresources/assets to play particularly well with Chrome's HTTP heuristics, even if it requires contortions that make the downloads slower in other browsers.
5) Write your code to rely on specific behavior in Chrome's HTML prescan, even if it requires contortions that break HTML prescans in other browsers.
That sort of thing.
Basically, if you just write some code, chances are it will run in times X, Y, Z in three different browsers, with the times closer or further apart depending on what features you're using and how the browsers optimized them, etc. But if you then set out to make it faster in X at the expense of any other considerations, you can get it to look like 0.9X, 2Y, 2Z. Or in some pathological cases 0.5X, 10Y, 10Z...