Bug 305703 [Viewers][CommonNavigator] remembered contributions can leak when using filters
bundles/org.eclipse.ui.navigator/src/org/eclipse/ui/internal/navigator/NavigatorContentService.java
listeners.remove(aListener);
	}
	/*
	 * (non-Javadoc)
	 * 
	 * @see java.lang.Object#toString()
	 */
	public String toString() {
		return "ContentService[" + viewerDescriptor.getViewerId() + "]"; 
	}
	private void notifyListeners(final NavigatorContentExtension aDescriptorInstance) {
		if (listeners.size() == 0) {
			return;
		}
		final List failedListeners = new ArrayList();
		for (Iterator listenersItr = listeners.iterator(); listenersItr.hasNext();) {
			final INavigatorContentServiceListener listener = (INavigatorContentServiceListener) listenersItr
					.next();
			SafeRunner.run(new NavigatorSafeRunnable() {
				public void run() throws Exception {
					listener.onLoad(aDescriptorInstance);
				}
				public void handleException(Throwable e) {
					super.handleException(e);
					failedListeners.add(listener);
				}
			});
		}
		if (failedListeners.size() > 0) {
			listeners.removeAll(failedListeners);