[Ajedi32]

Ironically, the section of the HTTP spec they initially referenced in that Chrome bug as justification for closing it as WontFix is precisely the part which explains why Chrome's current behavior is incorrect. Specifically:

> History mechanisms and caches are different. In particular history mechanisms SHOULD NOT try to show a semantically transparent view of the current state of a resource. Rather, a history mechanism is meant to show exactly what the user saw at the time when the resource was retrieved.

Doesn't matter whether a Vary header is sent or not; when a user clicks the back button they should see exactly what they saw when they previously viewed that page; regardless of whether that content is cached or not.