Make index provisional API.

pkg/analysis_server/lib/src/services/index/indexable_element.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 src.services.index;
 
 import 'dart:collection';
 
-import 'package:analysis_server/plugin/index/index_core.dart';
+import 'package:analysis_server/src/provisional/index/index_core.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/utilities_general.dart';
 
 /**
  * A wrapper around an [Element] that implements the [IndexableObject] interface.
  */
 class IndexableElement implements IndexableObject {
   /**
@@ skipping 145 matching lines @@
       ClassElement classElement = element.enclosingElement;
       int constructorIndex = classElement.constructors.indexOf(element);
       return _constructorKinds.putIfAbsent(constructorIndex,
           () => new IndexableElementKind._(ElementKind.CONSTRUCTOR));
     }
     ElementKind elementKind = element.kind;
     return _kindMap.putIfAbsent(
         elementKind, () => new IndexableElementKind._(elementKind));
   }
 }