Deduplicate childUpdate events based on transaction and appliedness

Previously, they were only being deduplicated based on the transaction,
which meant that an undo was seen as a duplicate (but then if you undid
again, that wasn't a duplicate).

Change-Id: If432ea28e6c206a2ad5562e529e2d3ed808c20e4
Merge "Deduplicate childUpdate events based on transaction and appliedness"