FirestoreAdapter onDocumentModified doesn't update data on position change

[s-hliao]

Steps to Reproduce:

• Set the FirestoreAdapter to a query capable of reaching two documents
• Attach adapter to a fully-implemented recyclerview capable of displaying data
• Update one document's data such that its position changes

Problem: Though the document is moved to the correct position, the data that was changed will not be updated in the recyclerView.

Current Solution: Added the line notifyItemChanged(change.getNewIndex()); at the end of the case in onDocumentModified to update data on modified document.

[samtstern]

@s-hliao this seems to be mentioning Android concepts but you filed this on the repo for the web codelab. Please re-file this on the correct repository.