This script keeps track of the current size of the screen. When the aspect ratio changes, it notifies all DeviceOrientationListeners in the scene. There only needs to be one of these in the scene. The new screen width and height are passed to the listeners when the orientation changes.
void FindAllListeners ()
This is called on Start to find all listeners in the scene. It can be called at other times if new listeners are added after the scene begins.