Generate constants in server as we do in plugin

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.
 
 import 'package:analysis_server/protocol/protocol.dart';
+import 'package:analysis_server/protocol/protocol_constants.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
-import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/context_manager.dart';
 import 'package:analysis_server/src/domain_analysis.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer/src/lint/linter.dart';
 import 'package:analyzer/src/services/lint.dart';
 import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:linter/src/rules.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../analysis_abstract.dart';
 import '../mocks.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(NotificationErrorsTest);
   });
 }
 
 @reflectiveTest
 class NotificationErrorsTest extends AbstractAnalysisTest {
   Map<String, List<AnalysisError>> filesErrors = {};
 
   void processNotification(Notification notification) {
-    if (notification.event == ANALYSIS_ERRORS) {
+    if (notification.event == ANALYSIS_NOTIFICATION_ERRORS) {
       var decoded = new AnalysisErrorsParams.fromNotification(notification);
       filesErrors[decoded.file] = decoded.errors;
     }
   }
 
   @override
   void setUp() {
     generateSummaryFiles = true;
     registerLintRules();
     super.setUp();
@@ skipping 96 matching lines @@
 ''');
     await waitForTasksFinished();
     await pumpEventQueue();
     List<AnalysisError> errors = filesErrors[testFile];
     expect(errors, hasLength(1));
     AnalysisError error = errors[0];
     expect(error.severity, AnalysisErrorSeverity.WARNING);
     expect(error.type, AnalysisErrorType.STATIC_WARNING);
   }
 }