Extension of IWorkbenchWindowPulldownDelegate that allows the delegate dropdown
menu to be a child of a Menu item. Necessary for CoolBar support. If a coolbar
group of items is not fully displayed, a chevron and a drop down menu will be
used to show the group's tool items. Therefore, a getMenu(Menu) method is necessary,
since the delegate drop down menu will be a child of the chevron menu item (not
the tool control).
Returns the menu for this pull down action. This method will only be
called if the user opens the pull down menu for the action. Note that it
is the responsibility of the implementor to properly dispose of any SWT
menus created by this method.