[SyncFS] Add RemoteToLocalSyncer skeleton

chrome/browser/sync_file_system/drive_backend/metadata_database.cc

Index: chrome/browser/sync_file_system/drive_backend/metadata_database.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/metadata_database.cc b/chrome/browser/sync_file_system/drive_backend/metadata_database.cc
index 737ded8eef07dc4ceac5a5e09030da835d0efaa4..d768e8293a6259e4f6b18338a08c6631fb0b681f 100644
--- a/chrome/browser/sync_file_system/drive_backend/metadata_database.cc
+++ b/chrome/browser/sync_file_system/drive_backend/metadata_database.cc
@@ -895,6 +895,19 @@ void MetadataDatabase::UpdateTracker(int64 tracker_id,
   WriteToDatabase(batch.Pass(), callback);
 }
 
+bool MetadataDatabase::GetNormalPriorityDirtyTracker(FileTracker* tracker) {
+  // TODO(tzik): Split |dirty_trackers| to |normal_priority_dirty_trackers|
+  // and |low_priority_dirty_trackers|.
+  // Add a function to mark a dirty tracker low priority.
+  NOTIMPLEMENTED();
+  return false;
+}
+
+bool MetadataDatabase::GetLowPriorityDirtyTracker(FileTracker* tracker) {
+  NOTIMPLEMENTED();
+  return false;
+}
+
 MetadataDatabase::MetadataDatabase(base::SequencedTaskRunner* task_runner)
     : task_runner_(task_runner), weak_ptr_factory_(this) {
   DCHECK(task_runner);