A week back, chrome 66 was released, but game isnt updated, so only browser's update could be the reason(if it is laggy), but i havnt got this report from QA.
Always try to clear browser's cache time to time.
We cant really control browser's updates, some updates are beneficial for webgl, while some not.
We are currently focussed on steam port & only working on it, the goal of which is to remove jerkyness. Announcing its "Coming soon" next week