always return solid background for listbox

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@30650 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/listbox.h

@@ -143,6 +143,11 @@ public:
 protected:
     WXDWORD MSWGetStyle(long style, WXDWORD *exstyle) const;
 
+    virtual WXHBRUSH MSWControlColor(WXHDC pDC)
+    {
+        return MSWControlColorSolid(pDC);
+    }
+
     // free memory (common part of Clear() and dtor)
     void Free();