split wxSizer::Fit() into ComputeFittingWindow/ClientSize() that only does computations and Fit() that applies the result to the window

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@51767 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/sizer.h

@@ -601,6 +601,9 @@ public:
 
     virtual void Layout();
 
+    wxSize ComputeFittingClientSize(wxWindow *window);
+    wxSize ComputeFittingWindowSize(wxWindow *window);
+
     wxSize Fit( wxWindow *window );
     void FitInside( wxWindow *window );
     void SetSizeHints( wxWindow *window );