getKeyboardRows function
Returns a list of VirtualKeyboard rows with VirtualKeyboardKey objects.
Implementation
List<List<VirtualKeyboardKey>> getKeyboardRows(
    VirtualKeyboardLayoutKeys layoutKeys) {
  // Generate lists for each keyboard row.
  return List.generate(layoutKeys.activeLayout.length,
      (int rowNum) => getKeyboardRowKeys(layoutKeys, rowNum));
}