[sync] Add backup time in synced device info so that server can flag device

chrome/browser/sync/profile_sync_service.h

Index: chrome/browser/sync/profile_sync_service.h
diff --git a/chrome/browser/sync/profile_sync_service.h b/chrome/browser/sync/profile_sync_service.h
index d4e85ef5ee2184c3d4a06f0efc5b389169214bee..91730f4cf83fffdd0a2ef0363d9c482dbcac4b8a 100644
--- a/chrome/browser/sync/profile_sync_service.h
+++ b/chrome/browser/sync/profile_sync_service.h
@@ -769,6 +769,8 @@ class ProfileSyncService : public ProfileSyncServiceBase,
   void SetClearingBrowseringDataForTesting(
       base::Callback<void(Profile*, base::Time, base::Time)> c);
 
+  base::Time GetDeviceBackupTimeForTesting() const;
+
  protected:
   // Helper to configure the priority data types.
   void ConfigurePriorityDataTypes();
@@ -944,6 +946,12 @@ class ProfileSyncService : public ProfileSyncServiceBase,
   // Clear browsing data since first sync during rollback.
   void ClearBrowsingDataSinceFirstSync();
 
+  // Post background task to check sync backup DB state if needed.
+  void CheckSyncBackupIfNeeded();
+
+  // Callback to receive backup DB check result.
+  void CheckSyncBackupCallback(base::Time backup_time);
+
  // Factory used to create various dependent objects.
   scoped_ptr<ProfileSyncComponentsFactory> factory_;
 
@@ -1110,6 +1118,10 @@ class ProfileSyncService : public ProfileSyncServiceBase,
 
   base::Callback<void(Profile*, base::Time, base::Time)> clear_browsing_data_;
 
+  // Last time when pre-sync data was saved. NULL pointer means backup data
+  // state is unknown. If time value is null, backup data doesn't exist.
+  scoped_ptr<base::Time> last_backup_time_;
+
   DISALLOW_COPY_AND_ASSIGN(ProfileSyncService);
 };