function simulateInsertionModification(tableSchema, rows) {
  var tx = mockStore.createTx(
      lf.TransactionType.READ_WRITE,
      [tableSchema],
      new lf.cache.Journal(hr.db.getGlobal(),
          lf.structs.set.create([tableSchema])));
  var table = tx.getTable(
      tableSchema.getName(),
      tableSchema.deserializeRow.bind(tableSchema),
      lf.backstore.TableType.DATA);
  table.put(rows);
  return tx.commit();
}
Simulates an external insertion/modification change.
@param {!lf.schema.Table} tableSchema
@param {!Array<!lf.Row>} rows The rows to  be inserted/modified.
@return {!IThenable}