[SyncFS] Handlng active tracker ID in TrackerIDSet-style on disk DB

chrome/browser/sync_file_system/drive_backend/metadata_database_index_on_disk.cc

Index: chrome/browser/sync_file_system/drive_backend/metadata_database_index_on_disk.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/metadata_database_index_on_disk.cc b/chrome/browser/sync_file_system/drive_backend/metadata_database_index_on_disk.cc
index 096338ad3719a6aacaa9cfb17f6abc6cd3d2c2df..6afa05c997c61a6ac1f37d8490dde9a9f6914ac2 100644
--- a/chrome/browser/sync_file_system/drive_backend/metadata_database_index_on_disk.cc
+++ b/chrome/browser/sync_file_system/drive_backend/metadata_database_index_on_disk.cc
@@ -1075,8 +1075,9 @@ void MetadataDatabaseIndexOnDisk::ActivateInTrackerIDSetWithPrefix(
 
   std::string value;
   leveldb::Status status = db_->Get(active_tracker_key, &value);
-  int64 active_tracker_id;
-  if (status.ok() && base::StringToInt64(value, &active_tracker_id)) {
+  int64 active_tracker_id = kInvalidTrackerID;
+  if (status.IsNotFound() ||
+      (status.ok() && base::StringToInt64(value, &active_tracker_id))) {
     DCHECK(active_tracker_id != tracker_id);
     db_->Put(active_tracker_key, base::Int64ToString(tracker_id));
   }