sync: Track validity of about:sync fields

sync/internal_api/public/sessions/sync_session_snapshot.h

 // Copyright (c) 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_SESSIONS_SYNC_SESSION_SNAPSHOT_H_
 #define SYNC_INTERNAL_API_PUBLIC_SESSIONS_SYNC_SESSION_SNAPSHOT_H_
 
 #include <string>
 
 #include "base/basictypes.h"
@@ skipping 53 matching lines @@
   int num_encryption_conflicts() const;
   int num_hierarchy_conflicts() const;
   int num_simple_conflicts() const;
   int num_server_conflicts() const;
   SyncSourceInfo source() const;
   bool notifications_enabled() const;
   size_t num_entries() const;
   base::Time sync_start_time() const;
   bool retry_scheduled() const;
 
+  // Set iff this snapshot was not built using the default constructor.
+  bool is_initialized() const;
+
  private:
   ModelNeutralState model_neutral_state_;
   bool is_share_usable_;
   syncer::ModelTypeSet initial_sync_ended_;
   syncer::ModelTypePayloadMap download_progress_markers_;
   bool has_more_to_sync_;
   bool is_silenced_;
   int num_encryption_conflicts_;
   int num_hierarchy_conflicts_;
   int num_simple_conflicts_;
   int num_server_conflicts_;
   SyncSourceInfo source_;
   bool notifications_enabled_;
   size_t num_entries_;
   base::Time sync_start_time_;
   bool retry_scheduled_;
+
+  bool is_initialized_;
 };
 
 }  // namespace sessions
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_SESSIONS_SYNC_SESSION_SNAPSHOT_H_