private WALEdit createWALEditForReplicateSkipWAL(
      MiniBatchOperationInProgress<Mutation> miniBatchOp,
      List<Pair<NonceKey, WALEdit>> nonceKeyAndWALEdits) {
      if (nonceKeyAndWALEdits.isEmpty()) {
        return this.createWALEdit(miniBatchOp);
      }
      // for MutationBatchOperation, more than one nonce is not allowed
      assert nonceKeyAndWALEdits.size() == 1;
      WALEdit currentWALEdit = nonceKeyAndWALEdits.get(0).getSecond();
      return new WALEdit(currentWALEdit);
    }
When there is a SKIP_WAL {@link Mutation},we create a new {@link WALEdit} for replicating
to region replica,first we fill the existing {@link WALEdit} to it and then add the
{@link Mutation} which is SKIP_WAL to it.
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java