Bug 95217 [Commands] Remove experimental handlerSubmission element from the "org.eclipse.ui.commands" extension point
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/AbstractHandler.java
/**
	 * Those interested in hearing about changes to this instance of
	 * <code>IHandler</code>. This member is null iff there are no listeners
	 * attached to this handler. (Most handlers don't have any listeners, and
	 * this optimization saves some memory.)
	 */
	private List handlerListeners;
	/**
	 * @see IHandler#addHandlerListener(IHandlerListener)
	 */
	public void addHandlerListener(final IHandlerListener handlerListener) {
		if (handlerListener == null)
			throw new NullPointerException();
		if (handlerListeners == null)
			handlerListeners = new ArrayList();
		if (!handlerListeners.contains(handlerListener))
			handlerListeners.add(handlerListener);
	}
	/**
	 * The default implementation does nothing. Subclasses who attach listeners
	 * to other objects are encouraged to detach them in this method.
	 * 
	 * @see org.eclipse.core.commands.IHandler#dispose()
	 */
	public void dispose() {
		
	}
	/**
	 * Fires an event to all registered listeners describing changes to this