i tried that block 1, it is laggy, but if you enable "GPU rasterization" the force in all layers, in chrome://flags it's a little better. also your going to have to raise the gpu split(performance in the config) mines at 128 right now, you could try that or go higher, i don't recommend more than 256 tops. normally mines at 96 and i'm running gnome, i raised it to try the game.
it depends on the game, some run perfectly fine, others don't seem optimized or they have a lot of things going on(aka: trying to be to fancy).
thanks for the heads up on the site though, going to use for my niece.