chromium/chromeos/components/test/data/onc/policy/policy_wifi1_proxy.onc

{
  "NetworkConfigurations": [
    {
      "GUID": "policy_wifi1",
      "Type": "WiFi",
      "Name": "Managed wifi1",
      "ProxySettings": {
        "Type": "PAC",
        "PAC": "http://pac.foo.com/script.pac"
      },
      "Type": "WiFi",
      "WiFi": {
        "Security": "None"
      }
    }
  ],
  "Type": "UnencryptedConfiguration"
}