@Override
  protected void onLayoutChange(Layout oldValue, Layout newValue) {
    super.onLayoutChange(oldValue, newValue);
    // Editor tab will lose focus after switching to JCEF preview for some reason.
    // So we should explicitly request focus for our editor here.
    if (newValue == Layout.SHOW_PREVIEW) {
      requestFocusForPreview();
    }
  }
@Override
  protected void onLayoutChange(Layout oldValue, Layout newValue)