Google owns a lot, including GMail: http://en.wikipedia.org/wiki/List_of_Google_products

It's possible Chrome was bundled with something else you have/use and you didn't realize it. They have a whole thing with their GMail (which other, non-Google companies email companies use as their base) where you have chat and friends, etc. and/or some other site's default could be Chrome and if you don't have it and want to see their site need it (sort of like with Adobe .pdfs).