The WriteUnitOfWork commits batched writes (multiple CRUD ops to replicate together within a single applyOps oplog entry) through an OpObserver event. However, we start batched writes by instantiating the decorator within the WriteUnitOfWork's constructor. It would be more consistent to extend the OpObserver interface to include methods for starting and aborting batched writes. This would also remove the need for the WriteUnitOfWork class to depend on the BatchedWriterContext.