adapted background color for mac

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@10379 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/generic/treectlg.cpp

@@ -663,9 +663,7 @@ bool wxGenericTreeCtrl::Create(wxWindow *parent, wxWindowID id,
     SetValidator( validator );
 #endif
 
-#ifndef __WXMAC__
     SetBackgroundColour( wxSystemSettings::GetSystemColour( wxSYS_COLOUR_LISTBOX ) );
-#endif
 
 //  m_dottedPen = wxPen( "grey", 0, wxDOT );  too slow under XFree86
     m_dottedPen = wxPen( "grey", 0, 0 );