expose a way to drop ownership of a window from builder tree

Change-Id: I6f6bff32271ed1d6c328ba211a6b1249fda039dd

include/vcl/builder.hxx

@@ -297,6 +297,9 @@ public:
     OString get_by_window(const ::Window *pWindow) const;
     void delete_by_window(const ::Window *pWindow);
 
+    //release ownership of pWindow, i.e. don't delete it
+    void drop_ownership(const ::Window *pWindow);
+
     //apply the properties of rProps to pWindow
     static void set_properties(::Window *pWindow, const stringmap &rProps);
 

vcl/source/window/builder.cxx

@@ -2997,13 +2997,18 @@ void VclBuilder::delete_by_name(const OString& sID)
 }
 
 void VclBuilder::delete_by_window(const Window *pWindow)
+{
+    drop_ownership(pWindow);
+    delete pWindow;
+}
+
+void VclBuilder::drop_ownership(const Window *pWindow)
 {
     for (std::vector<WinAndId>::iterator aI = m_aChildren.begin(),
          aEnd = m_aChildren.end(); aI != aEnd; ++aI)
     {
         if (aI->m_pWindow == pWindow)
         {
-            delete aI->m_pWindow;
             m_aChildren.erase(aI);
             break;
         }