[SyncFS] Unconditionally demote remote file trackers on remote-to-local sync

chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc

Index: chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc b/chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc
index cdc6c3e5dbeb83d3029c9da6c5e3cf17c60ee0d6..e3b8208cff2034bb6a5efc3247cebbbdb4c40f68 100644
--- a/chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc
+++ b/chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc
@@ -399,10 +399,17 @@ bool MetadataDatabaseIndex::HasDemotedDirtyTracker() const {
   return !demoted_dirty_trackers_.empty();
 }
 
-void MetadataDatabaseIndex::PromoteDemotedDirtyTrackers() {
+void MetadataDatabaseIndex::PromoteDemotedDirtyTracker(int64 tracker_id) {
+  if (demoted_dirty_trackers_.erase(tracker_id) == 1)
+    dirty_trackers_.insert(tracker_id);
+}
+
+bool MetadataDatabaseIndex::PromoteDemotedDirtyTrackers() {
+  bool promoted = !demoted_dirty_trackers_.empty();
   dirty_trackers_.insert(demoted_dirty_trackers_.begin(),
                          demoted_dirty_trackers_.end());
   demoted_dirty_trackers_.clear();
+  return promoted;
 }
 
 size_t MetadataDatabaseIndex::CountDirtyTracker() const {