Add an ONC property for the third-party VPN provider extension ID

chromeos/network/onc/onc_validator_unittest.cc

Index: chromeos/network/onc/onc_validator_unittest.cc
diff --git a/chromeos/network/onc/onc_validator_unittest.cc b/chromeos/network/onc/onc_validator_unittest.cc
index add35723ae9ab0d3c63c96dfc394100aa795b1e1..8517f7175e09c77e1cefea802416580fdfec8ccd 100644
--- a/chromeos/network/onc/onc_validator_unittest.cc
+++ b/chromeos/network/onc/onc_validator_unittest.cc
@@ -208,6 +208,9 @@ INSTANTIATE_TEST_CASE_P(
                   false),
         OncParams("openvpn_with_password.onc",
                   &kNetworkConfigurationSignature,
+                  false),
+        OncParams("third_party_vpn.onc",
+                  &kNetworkConfigurationSignature,
                   false)));
 
 namespace {
@@ -348,6 +351,10 @@ INSTANTIATE_TEST_CASE_P(
         std::make_pair(OncParams("openvpn-missing-verify-x509-name",
                                  &kNetworkConfigurationSignature,
                                  false),
+                       ExpectStrictNotValid("")),
+        std::make_pair(OncParams("third-party-vpn-missing-extension-id",
+                                 &kNetworkConfigurationSignature,
+                                 false),
                        ExpectStrictNotValid(""))));
 
 // Strict validator returns INVALID. Liberal validator repairs.