Bug 182714 [Contributions] Improve toolbar configurability
bundles/org.eclipse.jface/src/org/eclipse/jface/action/ContributionManager.java
*/
	private boolean isDirty = true;
	/**
	 * Number of dynamic contribution items.
	 */
	private int dynamicItems = 0;
	/**
	 * The overrides for items of this manager
	 */
	private IContributionManagerOverrides overrides;
	/**
	 * Creates a new contribution manager.
	 */
	protected ContributionManager() {
		
	}
	/*
	 * (non-Javadoc) Method declared on IContributionManager.
	 */
	public void add(IAction action) {
		Assert.isNotNull(action, "Action must not be null"); 
		add(new ActionContributionItem(action));
	}
	/*
	 * (non-Javadoc) Method declared on IContributionManager.
	 */
	public void add(IContributionItem item) {
		Assert.isNotNull(item, "Item must not be null"); 
		if (allowItem(item)) {
			contributions.add(item);