replace 5 copies of size constraining code with one function

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@45657 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/window.h

@@ -378,6 +378,8 @@ protected:
     // should be called from OnInternalIdle() if it's overridden
     void GTKUpdateCursor();
 
+    void ConstrainSize();
+
 private:
     enum ScrollUnit { ScrollUnit_Line, ScrollUnit_Page, ScrollUnit_Max };