Expandable textfield in header does not work properly in a <form>

It seems that the expandable textfield, such as the search buttons in the [layout examples](https://getmdl.io/components/index.html#layout-section), does not work correctly if you surround the `` with a ``, i.e. the button would no longer expand to reveal the text box.

Is there a way around this? I ended up writing a handler in JavaScript to capture the ENTER keypress for the search box and then generate a `` with the correct inputs populated and then submit the form.