Update 'search.getTypeHierarchy' to the latest spec.

pkg/analysis_services/lib/constants.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.constants;
 
 //
 // Property names
 //
 const String ADDED = 'added';
@@ skipping 13 matching lines @@
 const String ELEMENT_DESCRIPTION = 'elementDescription';
 const String ELEMENT_KIND = 'elementKind';
 const String EXCLUDED = 'excluded';
 const String ERROR = 'error';
 const String ERRORS = 'errors';
 const String FATAL = 'fatal';
 const String FILE = 'file';
 const String FILES = 'files';
 const String FIXES = 'fixes';
 const String FLAGS = 'flags';
-const String HIERARCHY = 'hierarchy';
+const String HIERARCHY_ITEMS = 'hierarchyItems';
 const String HOVERS = 'hovers';
 const String ID = 'id';
 const String INCLUDE_POTENTIAL = 'includePotential';
 const String INCLUDED = 'included';
 const String INTERFACE_MEMBERS = 'interfaceMembers';
 const String INTERFACES = 'interfaces';
 const String IS_ABSTRACT = 'isAbstract';
 const String IS_DEPRECATED = 'isDeprecated';
 const String IS_POTENTIAL = 'isPotential';
 const String IS_STATIC = 'isStatic';
@@ skipping 36 matching lines @@
 const String START_COLUMN = 'startColumn';
 const String START_LINE = 'startLine';
 const String STATIC_TYPE = 'staticType';
 const String SUBCLASSES = 'subclasses';
 const String SUBSCRIPTIONS = 'subscriptions';
 const String SUPERCLASS = 'superclass';
 const String SUPER_CLASS_MEMBER = 'superclassMember';
 const String TARGETS = 'targets';
 const String TYPE = 'type';
 const String VERSION = 'version';