anchor.diff:    styleUrls: const ['focus_trap.scss.css'],
     directives: const [FocusContentWrapper, AutoFocusDirective],
     changeDetection: ChangeDetectionStrategy.OnPush,
  -  // TODO(google): Change to `Visibility.local` to reduce code size.
  -  visibility: Visibility.all,
   )
   class FocusTrapComponent implements OnDestroy {
     final _disposer = new Disposer.oneShot();
  
positive.code:     _disposer.dispose();
    }
  
    focusFirst() {
      _focusFirstInOrder(
          new DomTreeIterator(_content.element, scope: _content.element));
    }
  
    focusLast() {
      _focusFirstInOrder(new DomTreeIterator(_content.element,
          scope: _content.element, reverse: true, wraps: true));
    }
  
    _focusFirstInOrder(Iterator<Element> iterator) {
      while (iterator.moveNext()) {
        if (iterator.current.tabIndex == 0 && _visible(iterator.current)) {
          iterator.current.focus();
  
negative.code: 
  @Directive(
    selector: '[focusContentWrapper]',
  )
  class FocusContentWrapper extends FocusableDirective {
    Element _element;
  