Merge two constants.dart into one.

pkg/analysis_server/test/analysis/notification_errors_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.analysis.notification_errors;
 
 import 'package:analysis_server/src/computer/error.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/domain_analysis.dart';
 import 'package:analysis_server/src/protocol.dart';
-import 'package:analysis_server/src/services/constants.dart';
 import 'package:analysis_testing/reflective_tests.dart';
 import 'package:unittest/unittest.dart';
 
 import '../analysis_abstract.dart';
 
 
 main() {
   groupSep = ' | ';
   runReflectiveTests(NotificationErrorsTest);
 }
@@ skipping 58 matching lines @@
 
 main() {
   print(V);
 }
 ''');
     return waitForTasksFinished().then((_) {
       expect(filesErrors[otherFile], isNull);
     });
   }
 }