Catch only the WinEventAct for the event notifier for process completion

This is necessary to filter out events like ThreadChange. The documentation
writes "The object is moved to another thread. This is the last event sent to
this object in the previous thread.". See the following url for details:

http://qt-project.org/doc/qt-5.0/qtcore/qevent.html#Type-enum

Change-Id: I091a4c1fe7f64337835e8ee1492c47cc73322fdc
Reviewed-by: Sergey Belyashov <Sergey.Belyashov@gmail.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>