code: private void trackFilters(final BundleContext bundleContext) {
  		final ServiceTracker<Filter, FilterWebElement> filterTracker = FilterTracker
  				.createTracker(extenderContext, bundleContext);
  
  		filterTracker.open();
  		trackers.add(0, filterTracker);
  
  		// FIXME needed?
  		final ServiceTracker<FilterMapping, FilterMappingWebElement> filterMappingTracker = FilterMappingTracker
  				.createTracker(extenderContext, bundleContext);
  
  		filterMappingTracker.open();
  		trackers.add(0, filterMappingTracker);
  	}
docs: Track filters.
  
  @param bundleContext the BundleContext associated with this bundle