Method _updateDirectDescendants

src/material/menu/menu.ts:514–521

* Sets up a stream that will keep track of any newly-added menu items and will update the list * of direct descendants. We collect the descendants this way, because `_allItems` can include * items that are part of child menus, and using a custom way of registering items is unreliable * when

()

   * when it comes to maintaining the item order.
   */
  private _updateDirectDescendants() {
    this._allItems.changes
      .pipe(startWith(this._allItems))
      .subscribe((items: QueryList<MatMenuItem>) => {
        this._directDescendantItems.reset(items.filter(item => item._parentMenu === this));
        this._directDescendantItems.notifyOnChanges();
      });
  }

  /** Gets the menu panel DOM node. */
  private _resolvePanel(): HTMLElement | null {