add todo

Author: Brian Chen

firebase-firestore/src/main/java/com/google/firebase/firestore/local/IndexBackfillerDelegate.java

@@ -17,6 +17,7 @@
 import com.google.firebase.firestore.index.IndexEntry;
 import javax.annotation.Nullable;
 
+// TODO: Update with IndexEntry signatures once they've been fleshed out.
 /**
  * Persistence layers intending to perform index backfills should implement this interface. This
  * interface defines the operations that the Index Backfiller needs from the persistence layer.

firebase-firestore/src/test/java/com/google/firebase/firestore/local/MemoryIndexBackfillerTest.java

@@ -1,4 +1,4 @@
-// Copyright 2018 Google LLC
+// Copyright 2021 Google LLC
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.