Chrome isn't open source.
Chromium is.
Certain parts of Chrome are released under both the BSD license, and the Google Terms of Use.
https://chrome.google.com/extensions/detail/gighmmpiobklfepjocnamgkkbiglidomfirefox - because it has adblock
i have yet to see a capable ad-blocking solution for chrome or I.E.
https://chrome.google.com/extensions/detail/cfhdojbkjhnklbpkdaibdccddilifddb