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
private void postProcessExtensions(Map groupIDsToEntries,
			Map entryIDsToEntries, Collection attributeMappings) {
		processGroupingEntries(groupIDsToEntries);
		processAttributeMappings(entryIDsToEntries, attributeMappings);
		postProcessContentGenerators();
	}
	/**
	 * Set up the fields and filters
	 */
	private void postProcessContentGenerators() {
		Iterator generatorIterator = generators.values().iterator();
		while (generatorIterator.hasNext()) {
			MarkerContentGenerator generator = (MarkerContentGenerator) generatorIterator
					.next();
			generator.initializeFromConfigurationElement(this);
		}
	}
	/**
	 * Process the grouping entries into thier required grouping entries.
	 * 
	 * @param groupingEntries
	 */
	private void processGroupingEntries(Map groupingEntries) {
		Iterator entriesIterator = groupingEntries.keySet().iterator();
		while (entriesIterator.hasNext()) {
			String nextGroupId = (String) entriesIterator.next();
			Iterator nextEntriesIterator = ((Collection) groupingEntries
					.get(nextGroupId)).iterator();
			if (markerGroups.containsKey(nextGroupId)) {
				while (nextEntriesIterator.hasNext()) {