CssState: avoid spurious timing-related test failure
If scrollbar needed, make popup widget display it instead of popup wrapper.
Partially reverts 4d1ddb9738c5a9af31092562211d8f0d4bec202c.
Fixes #266.
popup: various test cleanup / modernization, plus bug fix
popup: stop calling evt.preventDefault() on touchend.
It's not needed and actually prevents closing popups (on iOS 7).
Fixes #269.