give the generic tree and list controls a DoGetBestSize

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@28910 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/generic/treectlg.h

@@ -391,6 +391,8 @@ public:
     void OnGetToolTip( wxTreeEvent &event );
     void OnInternalIdle( );
 
+    virtual wxSize DoGetBestSize() const;
+
     virtual wxVisualAttributes GetDefaultAttributes() const
     {
         return GetClassDefaultAttributes(GetWindowVariant());