inglis-dl authored Jul 17, 2013 and David Gobbi committed Jul 18, 2013

Currently, the style will correctly pass on Start, Reset and End
events if there is an observer and HandleObservers is true.  The
WindowLevel event will never be passed on to an observer because
the style searches for, finds, and assigns the CurrentImageProperty
ivar during the StartWindowLevelEvent.

Change-Id: I561346c48889cf54f903af54e7d4f4f80e8484c2