I would pay actual money to help get a feature like that into Chromium or Firefox. Hell, if Firefox added that exact feature I might actually rethink my decision to switch to Chrome once they drop support for all the addons I use.
With this pref enabled, advertiser X will serve you different cookies on site A and B. They won't be able to track your browsing history from site to site. However, this breaks a lot of sites that depend on third-party services for login authentication or comment systems.
Here is the Firefox bug where you can report broken sites:
Essentially building a new container per origin.