To create a context menu for a view use something like:
MenuManager contextMenu = new MenuManager();
Control control = viewer.getControl();
Menu menu = contextMenu.createContextMenu(control);
control.setMenu(menu);
getSite().registerContextMenu("menu id", contextMenu, viewer);
where viewer
is the outline tree viewer.
The final registerContextMenu
call means that you can contribute to this menu using the menu id you specify.