Clear 'referenceMap' before summarizing a new unit.

pkg/analyzer/test/src/test_all.dart

 // Copyright (c) 2015, 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 analyzer.test.src.test_all;
 
 import 'package:unittest/unittest.dart';
 
 import '../utils.dart';
 import 'context/test_all.dart' as context;
 import 'plugin/plugin_config_test.dart' as plugin;
+import 'summary/test_all.dart' as summary;
 import 'task/test_all.dart' as task;
 import 'util/test_all.dart' as util;
 
 /// Utility for manually running all tests.
 main() {
   initializeTestEnvironment();
   group('src tests', () {
     context.main();
     plugin.main();
+    summary.main();
     task.main();
     util.main();
   });
 }