Bug 167170 [Markers] Need to check for duplicate filter names
M3 It is currently possible to enter duplicate filter names
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/DialogMarkerFilter.java
protected void updateForSelection() {
		updateEnabledState(true);
		markDirty();
	}
	/**
	 * Get all of the marker types avilable for the filter
	 * 
	 * @param selected
	 * @return Object[]
	 */
	Object[] getRootEntries(MarkerFilter selected) {
		List roots = selected.getRootTypes();
		List markerNodes = new ArrayList();
		HashMap categories = new HashMap();
		for (int i = 0; i < roots.size(); i++) {
			Object obj = roots.get(i);
			buildTypeTree(markerNodes, obj, categories);
		}
		return markerNodes.toArray();
	}
	/**
	 * Build the list of types and categories from the supplied object
	 * 
	 * @param elements
	 * @param obj
	 * @param categories
	 */
	private void buildTypeTree(List elements, Object obj, HashMap categories) {
		if (obj instanceof MarkerType) {
			MarkerType markerType = (MarkerType) obj;