[SyncFS] Fix unexpected delay on running sync task

chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/sync_file_system/drive_backend/metadata_database_index.h"
 
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 398 matching lines @@
 
 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 {
-  return dirty_trackers_.size() + demoted_dirty_trackers_.size();
+  return dirty_trackers_.size();
 }
 
 size_t MetadataDatabaseIndex::CountFileMetadata() const {
   return metadata_by_id_.size();
 }
 
 size_t MetadataDatabaseIndex::CountFileTracker() const {
   return tracker_by_id_.size();
 }
 
@@ skipping 313 matching lines @@
 
     DVLOG(3) << "  Remove from dirty_trackers_: " << tracker_id;
     dirty_trackers_.erase(tracker_id);
 
     demoted_dirty_trackers_.erase(tracker_id);
   }
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system