Define CellularPanel::Root

src/TrackPanel.h

@@ -337,6 +337,10 @@ protected:
    void MakeParentModifyState(bool bWantsAutoSave);    // if true, writes auto-save file. Should set only if you really want the state change restored after
                                                                // a crash, as it can take many seconds for large (eg. 10 track-hours) projects
 
+   // Get the root object defining a recursive subdivision of the panel's
+   // area into cells
+   std::shared_ptr<TrackPanelNode> Root() override;
+
    // Find track info by coordinate
    FoundCell FindCell(int mouseX, int mouseY) override;