I have a game that is only 11mb right now, but after finally wrapping the game with CocoonJS, I noticed the the game would go from 60fps to <15fps in about 10 seconds. I think the only way the game could be slowing down is having something like an infinite array; I have an array that I push to to get the direction of a swipe, then I set that array to an empty array to prevent an infinite array.