message: Dropdown follow wai-aria practices for expanding on arrow keys
diff: @@ -222,14 +222,22 @@ export default class Dropdown extends React.Component<IProps, IState> {
  this.close();
  break;
  case Key.ARROW_DOWN:
  + if (this.state.expanded) {
  this.setState({
  highlightedOption: this.nextOption(this.state.highlightedOption),
  });
  + } else {
  + this.setState({ expanded: true });
  + }
  break;
  case Key.ARROW_UP:
  + if (this.state.expanded) {
  this.setState({
  highlightedOption: this.prevOption(this.state.highlightedOption),
  });
  + } else {
  + this.setState({ expanded: true });
  + }
  break;
  default:
  handled = false;
  