Add test for new SetBackgroundColour() logic

which should leave the sunken border as it
   is a not give it a green border.


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@34213 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

samples/scroll/scroll.cpp

@@ -406,7 +406,8 @@ BEGIN_EVENT_TABLE( MyAutoScrollWindow, wxScrolledWindow)
 END_EVENT_TABLE()
 
 MyAutoScrollWindow::MyAutoScrollWindow( wxWindow *parent )
-    : wxScrolledWindow( parent )
+    : wxScrolledWindow( parent, -1, wxDefaultPosition, wxDefaultSize, 
+                        wxSUNKEN_BORDER|wxScrolledWindowStyle )
 {
     SetBackgroundColour( wxT("GREEN") );