Converted observatory flag-list element

runtime/observatory/lib/src/mocks/objects/flag.dart

 // Copyright (c) 2016, 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
 
 part of mocks;
 
-class TargetMock implements M.Target {
+class FlagMock implements M.Flag {
   final String name;
-  const TargetMock({this.name});
+  final String comment;
+  final bool modified;
+  final String valueAsString;
+
+  const FlagMock({this.name, this.comment, this.modified, this.valueAsString});
 }