As the article states, Chromium uses run-time checks (feature toggles) extensively. This lets half-baked features land and start undergoing testing before the feature is ready to be shown to the world.

But we don't say "oh no, this feature isn't ready, let's wrap it in checks". The feature is wrapped in checks from the very first commit, so that everything stays stable on master and on any release branches which are cut from master.

Then, when the feature is ready for prime-time, the developers working on it go through and remove the checks. So they don't accumulate in the codebase.