By default, an annotation object will return true if SupportsFill is true and Fill is not null or a transparent AnnBrush.
Derived objects can override this method to fine tune the return value.
Target Platforms: Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2