Make server use the common protocol classes

pkg/analysis_server/test/analysis/get_navigation_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_generated.dart';
 import 'package:analysis_server/src/domain_analysis.dart';
 import 'package:analyzer/file_system/file_system.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'notification_navigation_test.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(GetNavigationTest);
   });
 }
@@ skipping 223 matching lines @@
   _getNavigation(String file, int offset, int length) async {
     Request request = _createGetNavigationRequest(file, offset, length);
     Response response = await serverChannel.sendRequest(request);
     AnalysisGetNavigationResult result =
         new AnalysisGetNavigationResult.fromResponse(response);
     targetFiles = result.files;
     targets = result.targets;
     regions = result.regions;
   }
 }