createOverlayPaneSync method
Creates and returns an overlay pane DOM element.
Implementation
HtmlElement createOverlayPaneSync([OverlayState state = _defaultConfig]) {
// Create a detached DIV to use as the overlay host.
HtmlElement pane = DivElement()
..attributes['pane-id'] = _createUniqueId()
..classes.add(_paneClassName);
// Depending on the initial positioning, size, and visibility, apply the
// state properties to the detached element (we do not need to use a DOM
// write queue because it is not attached).
applyStateSync(state, pane);
containerElement.append(pane);
return pane;
}