Rename two more classes to prepare for the public API

pkg/analysis_server/lib/src/services/index/store/codec.dart

 // Copyright (c) 2014, 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 services.src.index.store.codec;
 
 import 'dart:collection';
 
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analyzer/src/generated/element.dart';
@@ skipping 163 matching lines @@
 }
 
 /**
  * A helper that encodes/decodes [Relationship]s to/from integers.
  */
 class RelationshipCodec {
   final StringCodec _stringCodec;
 
   RelationshipCodec(this._stringCodec);
 
-  Relationship decode(int idIndex) {
+  RelationshipImpl decode(int idIndex) {
     String id = _stringCodec.decode(idIndex);
-    return Relationship.getRelationship(id);
+    return RelationshipImpl.getRelationship(id);
   }
 
-  int encode(Relationship relationship) {
+  int encode(RelationshipImpl relationship) {
     String id = relationship.identifier;
     return _stringCodec.encode(id);
   }
 }
 
 /**
  * A helper that encodes/decodes [String]s from/to integers.
  */
 class StringCodec {
   /**
@@ skipping 17 matching lines @@
   int encode(String name) {
     int index = nameToIndex[name];
     if (index == null) {
       index = _indexToName.length;
       nameToIndex[name] = index;
       _indexToName.add(name);
     }
     return index;
   }
 }