[Sync] Log age of auth tokens on authentication failure

sync/internal_api/public/sync_manager.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_
 #define SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 43 matching lines @@
 
 // Used by SyncManager::OnConnectionStatusChange().
 enum ConnectionStatus {
   CONNECTION_OK,
   CONNECTION_AUTH_ERROR,
   CONNECTION_SERVER_ERROR
 };
 
 // Contains everything needed to talk to and identify a user account.
 struct SyncCredentials {
+  // The email associated with this account.
   std::string email;
+  // The raw authentication token's bytes.
   std::string sync_token;
+  // (optional) The time at which the token was fetched/refreshed.
+  base::Time sync_token_time;
 };
 
 // SyncManager encapsulates syncable::Directory and serves as the parent of all
 // other objects in the sync API.  If multiple threads interact with the same
 // local sync repository (i.e. the same sqlite database), they should share a
 // single SyncManager instance.  The caller should typically create one
 // SyncManager for the lifetime of a user session.
 //
 // Unless stated otherwise, all methods of SyncManager should be called on the
 // same thread.
@@ skipping 359 matching lines @@
   // Returns the SyncManager's encryption handler.
   virtual SyncEncryptionHandler* GetEncryptionHandler() = 0;
 
   // Ask the SyncManager to fetch updates for the given types.
   virtual void RefreshTypes(ModelTypeSet types) = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_SYNC_MANAGER_H_