Bug 55592 [Contributions] SubActionBars does not properly handle menu listeners
bundles/org.eclipse.jface/src/org/eclipse/jface/action/SubContributionManager.java
*/
	public void setVisible(boolean visible) {
		this.visible = visible;
		if (mapItemToWrapper.size() > 0) {
			Iterator enum = mapItemToWrapper.values().iterator();
			while (enum.hasNext()) {
				IContributionItem item = (IContributionItem) enum.next();
				item.setVisible(visible);
			}
			parentMgr.markDirty();
		}
	}
	/**
	 * Wraps a contribution item in a sub contribution item, and returns the new wrapper.
	 */
	protected SubContributionItem wrap(IContributionItem item) {
		return new SubContributionItem(item);
	}
	/**
	 * Unwrap a contribution item.
	 */
	protected IContributionItem unwrap(IContributionItem item) {
		if (item == null || item instanceof GroupMarker || item instanceof Separator) {
			return item;
		}
		Assert.isTrue(item instanceof SubContributionItem);
		return ((SubContributionItem) item).getInnerItem();
	}
}