Implement SearchEngine.searchAllSubtypes() with the analysis driver.

pkg/analysis_server/test/services/search/search_engine_test.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 test.services.src.search.search_engine_internal;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
@@ skipping 64 matching lines @@
   }
 
   test_searchAllSubtypes() async {
     _indexTestUnit('''
 class T {}
 class A extends T {}
 class B extends A {}
 class C implements B {}
 ''');
     ClassElement element = findElement('T');
-    ClassElement elementA = findElement('A');
-    ClassElement elementB = findElement('B');
-    ClassElement elementC = findElement('C');
-    var expected = [
-      _expectId(elementA, MatchKind.DECLARATION, 'A extends T'),
-      _expectId(elementB, MatchKind.DECLARATION, 'B extends A'),
-      _expectId(elementC, MatchKind.DECLARATION, 'C implements B')
-    ];
-    List<SearchMatch> matches = await searchEngine.searchAllSubtypes(element);
-    _assertMatches(matches, expected);
+    Set<ClassElement> subtypes = await searchEngine.searchAllSubtypes(element);
+    expect(subtypes, hasLength(3));
+    expect(subtypes, contains(predicate((ClassElement e) => e.name == 'A')));
+    expect(subtypes, contains(predicate((ClassElement e) => e.name == 'B')));
+    expect(subtypes, contains(predicate((ClassElement e) => e.name == 'C')));
   }
 
   test_searchMemberDeclarations() async {
     _indexTestUnit('''
 class A {
   test() {}
 }
 class B {
   int test = 1;
   int testTwo = 2;
@@ skipping 840 matching lines @@
     List<SearchMatch> matches = await searchEngine.searchReferences(element);
     _assertMatches(matches, expectedMatches);
     expect(matches, hasLength(expectedMatches.length));
   }
 
   static void _assertMatches(
       List<SearchMatch> matches, List<ExpectedMatch> expectedMatches) {
     expect(matches, unorderedEquals(expectedMatches));
   }
 }