Device robot refresh token integrity validation.

chrome/browser/policy/proto/cloud/device_management_backend.proto

Index: chrome/browser/policy/proto/cloud/device_management_backend.proto
diff --git a/chrome/browser/policy/proto/cloud/device_management_backend.proto b/chrome/browser/policy/proto/cloud/device_management_backend.proto
index 4f414bd341e28d7a425de2fac38a9c6826ff5cc0..18f1ea7f868ea907c43a9543d1c8479405e00b48 100644
--- a/chrome/browser/policy/proto/cloud/device_management_backend.proto
+++ b/chrome/browser/policy/proto/cloud/device_management_backend.proto
@@ -236,6 +236,10 @@ message PolicyData {
   // Indicates which public account or extension/plug-in this policy data is
   // for. See PolicyFetchRequest.settings_entity_id for more details.
   optional string settings_entity_id = 11;
+
+  // Indicates the identity the device service account is associated with.
+  // This is only sent as part of device policy fetch.
+  optional string service_account_identity = 12;
 }
 
 message PolicyFetchResponse {