Bug 214492 [Markers] Need to be able to add filters to existing markers views
Currently you can only add filters to a new markerContentProvider. We need to able to bind them to existing markerContentProviders as well.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/MarkerSupportRegistry.java
*            the markerAttributeGroupings found
	 * @see #postProcessExtensions(Map, Map, Collection)
	 */
	private void processExtension(IExtensionTracker tracker,
			IExtension extension, Map groupIDsToEntries, Map entryIDsToEntries,
			Collection attributeMappings) {
		IConfigurationElement[] elements = extension.getConfigurationElements();
		for (int j = 0; j < elements.length; j++) {
			IConfigurationElement element = elements[j];
			if (element.getName().equals(PROBLEM_FILTER)) {
				ProblemFilter filter = newFilter(element);
				registeredFilters.put(filter.getId(), filter);
				tracker.registerObject(extension, filter,
						IExtensionTracker.REF_STRONG);
				continue;
			}
			if (element.getName().equals(MARKER_GROUPING)) {
				String id = element
						.getAttribute(MarkerSupportConstants.ATTRIBUTE_ID);
				MarkerGroup group;
				if (id.equals(Util.TYPE_MARKER_GROUPING_ID))
					group = new TypeMarkerGroup(element.getAttribute(LABEL));
				else
					group = new MarkerGroup(element);
				markerGroups.put(group.getId(), group);
				tracker.registerObject(extension, group,
						IExtensionTracker.REF_STRONG);
				continue;
			}
			if (element.getName().equals(MARKER_GROUPING_ENTRY)) {