src/vs/platform/actions/common/actions.ts/MenuRegistryChangeEvent/merge
class MenuRegistryChangeEvent:	static merge(events: IMenuRegistryChangeEvent[]): IMenuRegistryChangeEvent {
		const ids = new Set<MenuId>();
		for (const item of events) {
			if (item instanceof MenuRegistryChangeEvent) {
				ids.add(item.id);
			}
		}
		return ids;
	}