Google s move to include the technology is a response to discussions with the White House earlier this year around privacy. The DNT system works in the background and sends a signal to Web sites, via a header, that the user does not want to be tracked with persistent cookies. Microsoft drew some criticism recently for its decision to enable Do Not Track by default in IE 10. Mozilla implemented the technology in Firefox in June 2011 when it released Firefox 5 and Microsoft has it in Internet Explorer, as well.
Source: https://threatpost.com/google-implements-do-not-track-chrome-23-110712/77193/