While logged in, visiting the frontend: Cache-Control: no-cache, must-revalidate, max-age=0, no-store, private

While logged in, visiting the backend: Cache-Control: no-cache, must-revalidate, max-age=0, no-store, private

While logged out, visiting the frontend: No Cache-Control header is present.

While logged out, visiting the backend and redirected to wp-login: Cache-Control: no-cache, must-revalidate, max-age=0

While logged in, visiting the backend, performing a logout, pressing the BACK button in the browser: No admin page is shown, but the login page.

LGTM!

Change looks good - looking at the spec it seems to make sense to have both.

Committed in https://core.trac.wordpress.org/changeset/55968