"Via: HTTP/1.1 GWA" HTTP header - what is it?

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http://serverfault.com – One of my customers has something installed on their site, which makes all their resources load from googleusercontent.com domain. All HTTP requests also have the following header: Via: HTTP/1.1 GWA All my searches of this particular header show "Google Web Accelerator", a client-side technology discontinued ca in 2006. I certainly don't have it installed (and even if I did, I'm pretty sure wget -S wouldn't make use of it). Can you point me to a product that's used on this website? It's likely some kind of cache like Cloudflare or Torbit, but from Google. (HowTos)