Maybe this will be helpfull.
Once I was making some game and was testing it on an old notebook. There chrome was overloaded CPU but Firefox not. After some investigation I found that the notebook had two GPU. One inbuild low pewerfull and other additional more powerfull. So OS or driver for some reason decide to use low powered GPU with Chrome (and use CPU to help the low GPU). And at the same time to use high powered GPU with Firefox.