Bug 293787 Markers view not filtering by workingsets
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/MarkerContentGenerator.java
/**
	 * Return all of the filters for the receiver.
	 * 
	 * @return Collection of MarkerFieldFilterGroup
	 */
	Collection getAllFilters() {
		if (filters == null) {
			filters = getDeclaredFilters();
			
			loadFiltersPreference();
		}
		return filters;
	}
	/**
	 * Return the currently enabled filters.
	 * 
	 * @return Collection of MarkerFieldFilterGroup
	 */
	Collection getEnabledFilters() {
		if (enabledFilters == null) {
			enabledFilters = new HashSet();
			Iterator filtersIterator = getAllFilters().iterator();
			while (filtersIterator.hasNext()) {
				MarkerFieldFilterGroup next = (MarkerFieldFilterGroup) filtersIterator
						.next();
				if (next.isEnabled())
					enabledFilters.add(next);
			}
		}
		return enabledFilters;