I don't understand how Chrome is worth "at least $15-$20 billion" when it's >99% FOSS. Developing Chromium is a giant money sink and the only reason it outperforms Firefox is that it's backed by a company willing to pay that bill.
If Chrome is sold, the buyer will be forced to either monetize it somehow (how? Remember how poorly that worked for Opera and Netscape before them?) or else to go non-profit with some other source of funding.
The Right™ option in this line of thinking would be to force a new Chrome Foundation non-profit and to either fine GOOG enough to establish an endowment for it or else to implement some sort of corporate tax on web/cloud services to fund it (or, at the corporation's discretion, Mozilla, whose primary funding comes from Google today and will likely dry up with this ruling).