Make server use the common protocol classes

pkg/analysis_server/test/analysis/notification_occurrences_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.occurrences;
-
 import 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.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(AnalysisNotificationOccurrencesTest);
   });
 }
@@ skipping 227 matching lines @@
   test_type_void() async {
     addTestFile('''
 void main() {
 }
 ''');
     await prepareOccurrences();
     int offset = findOffset('void main()');
     findRegion(offset, 'void'.length, false);
   }
 }