845e92835d
This fixes the patch for nginx to clear the Last-Modified header if a static file is served from the Nix store. So far we only used the ETag from the store path, but if the Last-Modified header is always set to "Thu, 01 Jan 1970 00:00:01 GMT", Firefox and Chrome/Chromium seem to ignore the ETag and simply use the cached content instead of revalidating. Alongside the fix, this also adds a dedicated NixOS VM test, which uses WebDriver and Firefox to check whether the content is actually served from the browser's cache and to have a more real-world test case.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at http://nixos.org/nixos and in the manual in doc/manual.