How is Chrome valued at $15-20 billion? The chromium part is free; and the added value of chrome that's not chromium, AFAICT, is mainly "integrates with Google products"—i.e., the parts that would get nuked in an antitrust action.
Chrome has 3.45 billion users worldwide.
As the gatekeeper between the user and the web, there's no shortage of to ways burn the good reputation of Chrome for one-time financial gains.