Don't call CacheBestSize() from DoGetBestSize() implementations

This is unnecessary, wxWindow::GetBestSize() already does this, so calling it
from DoGetBestSize() called by it too is just useless.

src/common/treebase.cpp

@@ -279,14 +279,9 @@ wxSize wxTreeCtrlBase::DoGetBestSize() const
     // need some minimal size even for empty tree
     if ( !size.x || !size.y )
         size = wxControl::DoGetBestSize();
-    else
-    {
-        // Add border size
+    else // add border size
         size += GetWindowBorderSize();
 
-        CacheBestSize(size);
-    }
-
     return size;
 }