paper-dropdown-menu demo behavior differences

[punch...@gmail.com]

If you try the demo for the paper-dropdown-menu, (on https://elements.polymer-project.org/elements/paper-dropdown-menu?view=demo:demo/index.html&active=paper-dropdown-menu) the dropdowns behave like regular html menus, as in if you click on an item that is already selected in the drop down list, the menu will go away.

If you download the element for paper-dropdown-menu, and run the same demo without that sidebar on the left, the menus work differently. If you choose an item that's already selected, the drop down list stays there. I fear this will be a big irritation for usability.

What are the differences in those two pages that make them behave differently? Is it because the page is wrapped in something that gives it this feature on the polymer-project website? I need to have my menus behave the same way.

Thanks