That should be enough to use it (in most cases).
There are also changes to xtra_res.* to have an xml-handler for wxScrollingdialog, so it can be used in xrc-files.
The xml-handler hast to be loaded before any xrc-is loaded (this is done in app.cpp).
And of course changes to wxSmith, so it "knows" wxScrollingDialog.
If you have a wxs- or xrc-file containing a scrollingdialog, you have to manually change the appropriate cbp-files, because wxSmith uses tem to determine the type of the main-widget.
If a dialog is loaded from xrc via LoadDialog, this has to be changed to LoadObject with classname wxScrollingDialog (you need the xrc-handler in this case).
I don't know the version I introduced all these changes in the debugger- and scintilla testbranch, but if you look for the version scrollingdialog.* appears the first time, you should have it.