Remove object variables for collections that have to be created dynam…

…ically eclipse-platform#2193

Since extensions can be added and removed and have to be considered when collecting marker fields, marker types, and marker groups,
we cannot create the collections once, we have to create them on demand.

bundles/org.eclipse.ui.ide/src/org/eclipse/ui/views/markers/internal/ContentGeneratorDescriptor.java

@@ -45,12 +45,8 @@ public class ContentGeneratorDescriptor {
 	private static final String MARKER_FIELD_REFERENCE = "markerFieldReference"; //$NON-NLS-1$
 
 	private IConfigurationElement configurationElement;
-	private MarkerField[] allFields;
-	private Collection<MarkerType> markerTypes;
 	private MarkerField[] initialVisible;
-	private Collection<MarkerGroup> groups;
 	private Collection<IConfigurationElement> generatorExtensions = new ArrayList<>();
-	private Map<String, MarkerType> allTypesTable;
 
 	/**
 	 * Create a new ContentGeneratorDescriptor
@@ -186,16 +182,15 @@ public MarkerField[] getInitialVisible() {
 	 * @return Collection of {@link MarkerGroup}
 	 */
 	public Collection<MarkerGroup> getMarkerGroups() {
-		if (groups == null) {
-			groups = new TreeSet<>((mg1, mg2) -> mg1.getMarkerField().getName().compareTo(mg2.getMarkerField().getName()));
+		Collection<MarkerGroup> groups = new TreeSet<>(
+				(mg1, mg2) -> mg1.getMarkerField().getName().compareTo(mg2.getMarkerField().getName()));
 
-			// Add the groups defined in the receiver
-			addDefinedGroups(groups);
+		// Add the groups defined in the receiver
+		addDefinedGroups(groups);
 
-			if (getId().equals(MarkerSupportRegistry.PROBLEMS_GENERATOR)) {
-				// Add the groups that reference the receiver.
-				groups.addAll(MarkerSupportRegistry.getInstance().getMarkerGroups());
-			}
+		if (getId().equals(MarkerSupportRegistry.PROBLEMS_GENERATOR)) {
+			// Add the groups that reference the receiver.
+			groups.addAll(MarkerSupportRegistry.getInstance().getMarkerGroups());
 		}
 		return groups;
 	}