Make server use the common protocol classes

pkg/analysis_server/test/search/top_level_declarations_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(TopLevelDeclarationsTest);
   });
 }
@@ skipping 53 matching lines @@
 ''');
     await findTopLevelDeclarations('^[A-E]\$');
     assertHasDeclaration(ElementKind.CLASS, 'A');
     assertHasDeclaration(ElementKind.CLASS, 'B');
     assertHasDeclaration(ElementKind.FUNCTION_TYPE_ALIAS, 'C');
     assertHasDeclaration(ElementKind.FUNCTION, 'D');
     assertHasDeclaration(ElementKind.TOP_LEVEL_VARIABLE, 'E');
     assertNoDeclaration(ElementKind.CLASS, 'ABC');
   }
 }