Method _registerCloseHandler

src/cdk/menu/menu-trigger.ts:311–319

* Subscribe to the MenuStack close events if this is a standalone trigger and close out the menu * this triggers when requested.

()

   * this triggers when requested.
   */
  private _registerCloseHandler() {
    if (!this._parentMenu) {
      this.menuStack.closed.pipe(takeUntil(this.destroyed)).subscribe(({item}) => {
        if (item === this.childMenu) {
          this.close();
        }
      });
    }
  }

  /**
   * Subscribe to the overlays outside pointer events stream and handle closing out the stack if a