Constructs a persistence helper object, usually associated with a
variant.
Parameters
variant
A COM object which implements IDispatch.
To be able to successfully call any of COMPersistHelper's methods, the object
has to implement IPersistFile, IPersistStream
and/or IPersistStreamInit.
Passing null as variant is only useful if the object is to be
loaded from a stream by calling COMPersistHelper::LoadFromStream.