function assertRowIdIndex(targetTable, serializedRows, expectedSize) {
  assertEquals(1, serializedRows.length);
  var rowIdIndex = lf.index.RowId.deserialize(
      targetTable.getRowIdIndexName(),
      serializedRows);
  assertEquals(expectedSize, rowIdIndex.getRange().length);
}
Asserts that the contents of the RowId index appear as expected in the
backing store.
@param {!lf.schema.Table} targetTable
@param {!Array<!lf.Row>} serializedRows The serialized version of the index.
@param {number} expectedSize The expected number of rowIds in the index.