Add wxTopLevelWindow::SetRepresentedFilename().

This currently is only implemented under OS X and sets the proxy icon there
but could be implemented to do something useful under the other platforms too
in the future.

Closes #13797.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@70295 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/osx/toplevel.h

@@ -77,6 +77,8 @@ public:
     virtual void OSXSetModified(bool modified);
     virtual bool OSXIsModified() const;
 
+    virtual void SetRepresentedFilename(const wxString& filename);
+
 protected:
     // common part of all ctors
     void Init();