Bug 270008 [CommonNavigator] Ability to extend bindings beyond "inheritsBindingsFrom" tag
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/extensions/NavigatorViewerDescriptor.java
* 
	 * @param aViewerId
	 *            The identifier for this descriptor.
	 */
	NavigatorViewerDescriptor(String aViewerId) {
		super();
		this.viewerId = aViewerId;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorViewerDescriptor#getViewerId()
	 */
	public String getViewerId() {
		return viewerId;
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see org.eclipse.ui.internal.navigator.extensions.INavigatorViewerDescriptor#getPopupMenuId()
	 */
	public String getPopupMenuId() {
		return popupMenuId != null ? popupMenuId : viewerId;
	}
	/**
	 * Consume an action binding for this viewer.
	 * 
	 * @param element
	 *            The IConfigurationElement containing a viewerActionBinding
	 *            element.