Add OCCURRENCES_CONTRIBUTOR_EXTENSION_POINT_ID.

pkg/analysis_server/lib/analysis/occurrences_core.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+library analysis_server.analysis.occurrences_core;

[Brian Wilkerson, 2015/09/11 20:26:24]

I would prefer to have this in a sub-directory named "occurrences".

+
+import 'package:analysis_server/src/protocol.dart' show Element, Occurrences;
+import 'package:analyzer/src/generated/engine.dart' show AnalysisContext;
+import 'package:analyzer/src/generated/source.dart' show Source;
+
+/**
+ * An object used to produce occurrences.
+ *
+ * Clients are expected to subtype this class when implementing plugins.
+ */
+abstract class OccurrencesContributor {
+  /**
+   * Contribute occurrences into the given [collector].
+   * The [context] can be used to get analysis results.
+   */
+  void computeOccurrences(
+      OccurrencesCollector collector, AnalysisContext context, Source source);
+}
+
+/**
+ * An object that [OccurrencesContributor]s use to record occurrences into.
+ *
+ * Clients are not expected to subtype this class.
+ */
+abstract class OccurrencesCollector {
+  /**
+   * Record a new element occurrences.
+   */
+  void addOccurrences(Occurrences occurrences);
+}