Bug 204458 [Commands] Allow menu and toolbars to fire execution events
Keybindings will currently fire execution events when executing actions from the action framework. i.e. IActions with their actionDefinitionId set and IActionDelegates with the definitionId attribute in their action contributions. But it would be nice if selecting the menu or tool item would also fire the equivalent events. PW
bundles/org.eclipse.core.commands/src/org/eclipse/core/commands/CommandManager.java
* The set of identifiers for those categories that are defined. This value
	 * may be empty, but it is never <code>null</code>.
	 */
	private final Set definedCategoryIds = new HashSet();
	/**
	 * The set of identifiers for those command parameter types that are
	 * defined. This value may be empty, but it is never <code>null</code>.
	 * 
	 * @since 3.2
	 */
	private final Set definedParameterTypeIds = new HashSet();
	/**
	 * The execution listener for this command manager. This just forwards
	 * events from commands controlled by this manager to listeners on this
	 * manager.
	 */
	private IExecutionListener executionListener = null;
	/**
	 * The collection of execution listeners. This collection is
	 * <code>null</code> if there are no listeners.
	 */
	private ListenerList executionListeners = null;
	/**
	 * The help context identifiers ({@link String}) for a handler ({@link IHandler}).
	 * This map may be empty, but it is never <code>null</code>. Entries are
	 * removed if all strong references to the handler are removed.
	 * 
	 * @since 3.2
	 */
	private final Map helpContextIdsByHandler = new WeakHashMap();