[SyncFS] Make MetadataDatabase operations synchronous

chrome/browser/sync_file_system/drive_backend/folder_creator.cc

Index: chrome/browser/sync_file_system/drive_backend/folder_creator.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/folder_creator.cc b/chrome/browser/sync_file_system/drive_backend/folder_creator.cc
index 6176ed4d1a8fb8039f96adfa12bafb979cb2f846..9bafa087b890ebb7358e709774cf2d6c3473a0a2 100644
--- a/chrome/browser/sync_file_system/drive_backend/folder_creator.cc
+++ b/chrome/browser/sync_file_system/drive_backend/folder_creator.cc
@@ -113,10 +113,10 @@ void FolderCreator::DidListFolders(
 
   std::string file_id = oldest->file_id();
 
-  metadata_database_->UpdateByFileResourceList(
-      candidates.Pass(), base::Bind(&FolderCreator::DidUpdateDatabase,
-                                    weak_ptr_factory_.GetWeakPtr(),
-                                    file_id, callback));
+  status = metadata_database_->UpdateByFileResourceList(candidates.Pass());
+
+  // TODO(tzik): Expand this function.
+  DidUpdateDatabase(file_id, callback, status);
 }
 
 void FolderCreator::DidUpdateDatabase(const std::string& file_id,