Bug 305703 [Viewers][CommonNavigator] remembered contributions can leak when using filters
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
* org.eclipse.ui.IMemento)
	 */
	public void saveState(final IMemento aMemento) {
		synchronized (this) {
			for (Iterator extensionItr = getExtensions().iterator(); extensionItr.hasNext();) {
				final NavigatorContentExtension element = (NavigatorContentExtension) extensionItr
						.next();
				SafeRunner.run(new NavigatorSafeRunnable(((NavigatorContentDescriptor) element
						.getDescriptor()).getConfigElement()) {
					public void run() throws Exception {
						element.saveState(aMemento);
					}
				});
			}
		}
	}
	public boolean isActive(String anExtensionId) {
		return assistant.isActive(anExtensionId);
	}
	public boolean isVisible(String anExtensionId) {
		return assistant.isVisible(anExtensionId);
	}
	protected final Collection getExtensions() {
		return (contentExtensions.size() > 0) ? Collections
				.unmodifiableCollection(contentExtensions.values())
				: Collections.EMPTY_LIST;
	}
	/*
	 * (non-Javadoc)
	 *