stable_sort(selected_items.begin(), selected_items.end(),
[](const shared_ptr<RowItem> &a, const shared_ptr<RowItem> &b) {
return a->visual_v_offset() < b->visual_v_offset(); });
shared_ptr<TraceGroup> group(new TraceGroup());
shared_ptr<RowItem> focus_item(
stable_sort(selected_items.begin(), selected_items.end(),
[](const shared_ptr<RowItem> &a, const shared_ptr<RowItem> &b) {
return a->visual_v_offset() < b->visual_v_offset(); });
shared_ptr<TraceGroup> group(new TraceGroup());
shared_ptr<RowItem> focus_item(