Update 'search.getTypeHierarchy' to the latest spec.

pkg/analysis_server/lib/src/search/search_domain.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 search.domain;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/computer/element.dart' as se;
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/protocol.dart';
 import 'package:analysis_server/src/search/element_references.dart';
 import 'package:analysis_server/src/search/search_result.dart';
 import 'package:analysis_server/src/search/type_hierarchy.dart';
 import 'package:analysis_services/constants.dart';
+import 'package:analysis_services/json.dart';
 import 'package:analysis_services/search/search_engine.dart';
 import 'package:analyzer/src/generated/element.dart';
 
 /**
  * Instances of the class [SearchDomainHandler] implement a [RequestHandler]
  * that handles requests in the search domain.
  */
 class SearchDomainHandler implements RequestHandler {
   /**
    * The analysis server that is using this handler to process requests.
@@ skipping 108 matching lines @@
     String file = request.getRequiredParameter(FILE).asString();
     int offset = request.getRequiredParameter(OFFSET).asInt();
     // prepare Element
     List<Element> elements = server.getElementsAtOffset(file, offset);
     if (elements.isEmpty) {
       return new Response(request.id);
     }
     Element element = elements.first;
     // prepare type hierarchy
     TypeHierarchyComputer computer = new TypeHierarchyComputer(searchEngine);
-    computer.compute(element).then((TypeHierarchyItem item) {
+    computer.compute(element).then((List<TypeHierarchyItem> items) {
       Response response = new Response(request.id);
-      response.setResult(HIERARCHY, item);
+      response.setResult(HIERARCHY_ITEMS, objectToJson(items));
       server.sendResponse(response);
     });
     // delay response
     return Response.DELAYED_RESPONSE;
   }
 
   @override
   Response handleRequest(Request request) {
     try {
       String requestName = request.method;
@@ skipping 20 matching lines @@
     notification.setParameter(ID, searchId);
     notification.setParameter(LAST, isLast);
     notification.setParameter(RESULTS, results);
     server.sendNotification(notification);
   }
 
   static SearchResult toResult(SearchMatch match) {
     return new SearchResult.fromMatch(match);
   }
 }