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
if (field != null)
			fields.put(element
					.getAttribute(MarkerSupportConstants.ATTRIBUTE_ID), field);
		tracker.registerObject(extension, field, IExtensionTracker.REF_STRONG);
	}
	/**
	 * Process the content generator defined in the extension.
	 * 
	 * @param tracker
	 * @param extension
	 * @param element
	 */
	private void processContentGenerator(IExtensionTracker tracker,
			IExtension extension, IConfigurationElement element) {
		MarkerContentGenerator generator = new MarkerContentGenerator(element);
		generators.put(generator.getId(), generator);
		tracker.registerObject(extension, generator,
				IExtensionTracker.REF_STRONG);
	}
	/**
	 * Process the cross references after all of the extensions have been read.
	 * 
	 * @param groupIDsToEntries
	 *            Mapping of group names to the markerGroupingEntries registered
	 *            for them
	 * @param entryIDsToEntries
	 *            Mapping of entry names to the mappings for them
	 * @param attributeMappings
	 *            the markerAttributeGroupings found
	 */