Make server use the common protocol classes

pkg/analysis_server/test/plugin/protocol_dart_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/plugin/protocol/protocol_dart.dart';
-import 'package:analysis_server/protocol/protocol_generated.dart';
 import 'package:analyzer/dart/ast/ast.dart' as engine;
 import 'package:analyzer/dart/ast/visitor.dart' as engine;
 import 'package:analyzer/dart/element/element.dart' as engine;
 import 'package:analyzer/dart/element/type.dart' as engine;
 import 'package:analyzer/error/error.dart' as engine;
 import 'package:analyzer/src/dart/ast/utilities.dart' as engine;
 import 'package:analyzer/src/dart/element/element.dart' as engine;
 import 'package:analyzer/src/error/codes.dart' as engine;
 import 'package:analyzer/src/generated/source.dart' as engine;
+import 'package:analyzer_plugin/protocol/protocol_common.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
 import '../abstract_context.dart';
 
 main() {
   defineReflectiveSuite(() {
     defineReflectiveTests(ElementTest);
     defineReflectiveTests(ElementKindTest);
   });
@@ skipping 442 matching lines @@
       expect(location.offset, 16);
       expect(location.length, 'mySetter'.length);
       expect(location.startLine, 2);
       expect(location.startColumn, 7);
     }
     expect(element.parameters, '(String x)');
     expect(element.returnType, isNull);
     expect(element.flags, 0);
   }
 }