protected JComponent createToolbar(JPanel parent, Tree tree) {
    DefaultActionGroup group = new DefaultActionGroup();
    group.add(new SetAsRootAction(tree));

    AnAction back = new GoBackwardAction();
    back.registerCustomShortcutSet(new CustomShortcutSet(KeyStroke.getKeyStroke(KeyEvent.VK_LEFT, InputEvent.ALT_MASK)), parent);
    group.add(back);

    AnAction forward = new GoForwardAction();
    forward.registerCustomShortcutSet(new CustomShortcutSet(KeyStroke.getKeyStroke(KeyEvent.VK_RIGHT, InputEvent.ALT_MASK)), parent);
    group.add(forward);

    ActionToolbar toolbar = ActionManager.getInstance().createActionToolbar("DebuggerTreeWithHistory", group, true);
    toolbar.setTargetComponent(tree);
    return toolbar.getComponent();
  }
protected JComponent createToolbar(JPanel parent, Tree tree)