neat, turning on "block third-party cookies" in Chrome prevents you from using HTTP/2 to track users across sites. blocking third-party cookies in Firefox doesn't prevent it, but setting "privacy.firstparty.isolate" does.
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chromestatus.com/feature/573077 covers properly splitting up all the connection pools, etc. Look at the issues on the tracked that it's blocked on.
At some point I had a link to one of their main design documents covering a lot of what had to be done but I can't find it anymore. The one in that thread is not what I'm talking about.