Make index provisional API.

pkg/analysis_server/lib/plugin/index/index.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.
-
-/**
- * Support for client code that extends the analysis server by adding new index
- * contributors.
- *
- * Plugins can register index contributors. The registered contributors will be
- * used to contribute relationships to the index when the analysis of a file has
- * been completed.
- *
- * Typical relationships include things like "this variable is referenced here"
- * or "this method is invoked here". The index is used to improve the
- * performance of operations such as search or building a type hierarchy by
- * pre-computing some of the information needed by those operations.
- *
- * If a plugin wants to contribute information to the index, it should implement
- * the class [IndexContributor] and then register the contributor by including
- * code like the following in the plugin's registerExtensions method:
- *
- *     @override
- *     void registerExtensions(RegisterExtension registerExtension) {
- *       ...
- *       registerExtension(
- *           INDEX_CONTRIBUTOR_EXTENSION_POINT_ID,
- *           new MyIndexContributor());
- *       ...
- *     }
- */
-library analysis_server.plugin.index.index;
-
-import 'package:analysis_server/plugin/index/index_core.dart';
-import 'package:analysis_server/src/plugin/server_plugin.dart';
-import 'package:plugin/plugin.dart';
-
-/**
- * The identifier of the extension point that allows plugins to register index
- * contributors. The object used as an extension must be an [IndexContributor].
- */
-final String INDEX_CONTRIBUTOR_EXTENSION_POINT_ID = Plugin.join(
-    ServerPlugin.UNIQUE_IDENTIFIER,
-    ServerPlugin.INDEX_CONTRIBUTOR_EXTENSION_POINT);