Bug 200316 [CommonNavigator] Can not contribute property page to classpath container in project explorer
bundles/org.eclipse.ui.navigator.resources/src/org/eclipse/ui/internal/navigator/resources/actions/PropertiesActionProvider.java
private ISelectionProvider delegate;
		private DelegateSelectionProvider(ISelectionProvider s) {
			delegate = s;
		}
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.jface.viewers.ISelectionProvider#addSelectionChangedListener(org.eclipse.jface.viewers.ISelectionChangedListener)
		 */
		public void addSelectionChangedListener(
				ISelectionChangedListener listener) {
			delegate.addSelectionChangedListener(listener);
		}
		/*
		 * (non-Javadoc)
		 * 
		 * @see org.eclipse.jface.viewers.ISelectionProvider#getSelection()
		 */
		public ISelection getSelection() {
			if (delegate.getSelection() instanceof IStructuredSelection) {