While poking through stuff for Power Pack, I noticed that movable region

comments were broken for things other than images. As I dug deeper, I

discovered at least one instance of some confusing API.
This change fixes three major issues:

We were calling 'onClicked' by hand without passing an event object.
The "selectionRegionSize" API was very confusing. I've changed the same of

  the setter to make it clear we're setting a function that returns the region

  size.
Fix a couple calls to _super that were causing infinite recursion.

Tested this in conjunction with a couple corresponding changes to Power Pack.