So this implies that Google (obviously) wants the world to use its Chrome browser. But it seems that the guys there in Mountain View are themselves yet to get used to their very own web browser and are still relying on Firefox for travelling across the World Wide Web.
I stumbled across this browsing through Google’s Search Engine Optimization Starter Guide [PDF link] (Dated November 13, 2008) [Via] and found that one of the screenshots (on page 3) that the good guys used to make things easier for us has a tiny but very identifiable Firefox logo. That can mean only one thing – Google still uses Firefox! And that is a good thing. Even Bill Gates might be.
To give them the benifit of doubt, they might be working on a Mac (I never worked on that much) and Google is yet to release a Mac-compatible version of Chrome. Therefore Firefox.