Issue 21650. Fix linked positions added after insert code buffers.

pkg/analysis_server/test/services/correction/fix_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.correction.fix;
 
 import 'package:analysis_server/src/protocol.dart' hide AnalysisError;
 import 'package:analysis_server/src/services/correction/fix.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/index/local_memory_index.dart';
@@ skipping 215 matching lines @@
 class A {
   A.named(int i, double d) {
   }
 
   method() {}
 }
 main() {
   new A.named(1, 2.0);
 }
 ''');
+    _assertLinkedGroup(
+        change.linkedEditGroups[0],
+        ['named(int ', 'named(1']);
   }
 
   void test_createConstructorSuperExplicit() {
     _indexTestUnit('''
 class A {
   A(bool p1, int p2, double p3, String p4, {p5});
 }
 class B extends A {
   B() {}
 }
@@ skipping 2099 matching lines @@
       positions.add(new Position(testFile, offset));
     }
     return positions;
   }
 
   void _indexTestUnit(String code) {
     resolveTestUnit(code);
     index.indexUnit(context, testUnit);
   }
 }