MS: Okay, gooogle, you win, we aren't good at making browsers like you are. Can you take on all the responsibility of making this browser work while we focus solely on what our customers want?
So they can basically blame Google for everything while spending all their time building on top of chrome.
For these reasons Microsoft did not win the browser war, because there is no war if there isn't anything financially important to fight over.
on edit: changed a was to were.
Google is definitely using Chrome for more than just a security measure. Google is getting aggressive in competing with Firefox, what they are doing is either borderline or literally illegal, like making their services intentionally slower or have a worse UI on Firefox.
They are doing it now to Firefox, so imagine what they will do if they have 100% marketshare in the browser industry. A competitor to YouTube is rising? Make their videos stream a bit slower. Or refuse to support new standard technologies, and support some deprecated ones that their websites still uses, forcing everyone to use Google's standard, and then slowly depricate those standards after secretly removing them from your services.
Phrasing it this way makes it obvious that this is illegal, but I'm sure they will find a way to subtlety do it so that a case can't be made against them, while still screwing their competitors.
PS: That's what most of these companies do.