Remove Expect from core library.

sdk/lib/_internal/dartdoc/test/dartdoc_search_test.dart

 // Copyright (c) 2012, 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 dartdoc_search_test;
 
 // TODO(rnystrom): Use "package:" URL (#4968).
+import '../../../../../pkg/expect/lib/expect.dart';
 import '../lib/src/dartdoc/nav.dart';
 import '../lib/src/client/search.dart';
 
 const String URL = 'dummy-url';
 
 testTopLevelVsMembers() {
         var search = new SearchText('timer');
         var match = obtainMatch(search, 'timer');
         // Matching a top-level field 'timer';
         var topLevelResult = new Result(match, FIELD, URL);
@@ skipping 25 matching lines @@
         var prefixResult = new Result(prefixMatch, FIELD, URL, type: 'Event');
         Expect.equals(-1, resultComparator(fullResult, prefixResult),
                 "Full matches should be preferred to prefix matches");
 }
 
 void main() {
         testTopLevelVsMembers();
         testTopLevelFullVsPrefix();
         testMemberFullVsPrefix();
 }