Generate constants in server as we do in plugin

pkg/analysis_server/test/analysis/notification_errors_test.dart

Index: pkg/analysis_server/test/analysis/notification_errors_test.dart
diff --git a/pkg/analysis_server/test/analysis/notification_errors_test.dart b/pkg/analysis_server/test/analysis/notification_errors_test.dart
index baa4f0260a43822ed56ddc9bd66bf86edb8f87f0..98539b31bc458bdf0bcadf1afcb0c50232918056 100644
--- a/pkg/analysis_server/test/analysis/notification_errors_test.dart
+++ b/pkg/analysis_server/test/analysis/notification_errors_test.dart
@@ -3,8 +3,8 @@
 // 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';
@@ -29,7 +29,7 @@ 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;
     }