Generate constants in server as we do in plugin

pkg/analysis_server/test/analysis/notification_highlights_test2.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 'dart:async';
 
 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:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../analysis_abstract.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(AnalysisNotificationHighlightsTest);
     defineReflectiveTests(HighlightTypeTest);
@@ skipping 69 matching lines @@
     }
     return length;
   }
 
   Future prepareHighlights() {
     addAnalysisSubscription(AnalysisService.HIGHLIGHTS, testFile);
     return _resultsAvailable.future;
   }
 
   void processNotification(Notification notification) {
-    if (notification.event == ANALYSIS_HIGHLIGHTS) {
+    if (notification.event == ANALYSIS_NOTIFICATION_HIGHLIGHTS) {
       var params = new AnalysisHighlightsParams.fromNotification(notification);
       if (params.file == testFile) {
         regions = params.regions;
         _resultsAvailable.complete(null);
       }
     }
   }
 
   @override
   void setUp() {
@@ skipping 994 matching lines @@
   void test_toString() {
     expect(HighlightRegionType.CLASS.toString(), 'HighlightRegionType.CLASS');
   }
 
   void test_valueOf_unknown() {
     expect(() {
       new HighlightRegionType('no-such-type');
     }, throws);
   }
 }