Google chrome's caching behaviours for css sub-resources fetched with `url()` is unexpectedly aggressive

Question

CSS looks ordinarily:

background-image: url(/path/to.png);

Caching on the server side is set to be cache-control: no-cache.

All resources are cached as expected (in cache, must revalidate), but sub-resources referred by url(...) in css stylesheets google chrome caches extremely agressively: the browser doesn't revalidate them.

That's how the dev tools look like for what I'm talking about:

Firefox works as expected: every resource is revalidated (and http 304 is returned).