To have better support for themed and custom backgrounds for wxMSW wxComboCtrl, use WS_EX_COMPOSITED and wxBG_STYLE_ERASE instead of custom double-buffering (when made possible by the OS version)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67276 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/combo.h

@@ -94,6 +94,8 @@ protected:
     void OnPaintEvent( wxPaintEvent& event );
     void OnMouseEvent( wxMouseEvent& event );
 
+    virtual bool HasTransparentBackground() { return IsDoubleBuffered(); }
+
 private:
     void Init();