Trivial Description
In MutationState#send, we always allocate the following:
List<TableRef> txTableRefs = Lists.newArrayListWithExpectedSize(mutations.size());
and if a table's transactional, we populate it:
txTableRefs.add(origTableRef);`
but this is never referred to again in either logic or logging, and it's a local variable so we can't be using it elsewhere either. It should be removed or used (and if used, it should only be allocated in the transactional use case.)