If we use components inherited from HBoxLayoutContainer, than we can found problem that when browser window isn't collapsed HBoxLayoutContainer.onUnoverflow method consumes many cpu time on layout by triggering timer every ~10ms. If we collapse window problem disappears and comes back after visibility change event on restoring window.

Also I've noticed that if we just move this method to child class - there is no timer event end corresponding cpu usage.

Here is screenshot with Google Chrome timeline.