Make server use the common protocol classes

pkg/analysis_server/test/search/element_references_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 'dart:async';
 
 import 'package:analysis_server/protocol/protocol.dart';
 import 'package:analysis_server/protocol/protocol_generated.dart';
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import 'abstract_search_domain.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ElementReferencesTest);
   });
 }
@@ skipping 647 matching lines @@
   T m() => null;
 }
 ''');
     await findElementReferences('T> {', false);
     expect(searchElement.kind, ElementKind.TYPE_PARAMETER);
     expect(results, hasLength(2));
     assertHasResult(SearchResultKind.REFERENCE, 'T f;');
     assertHasResult(SearchResultKind.REFERENCE, 'T m()');
   }
 }