Unify the server and plugin versions of the generators

pkg/analysis_server/benchmark/perf/benchmark_flutter.dart

 // Copyright (c) 2016, 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 server.performance.local;
 
 import 'dart:async';
 
-import 'package:analysis_server/plugin/protocol/protocol.dart';
+import 'package:analysis_server/protocol/protocol_generated.dart';
 
 import 'benchmark_scenario.dart';
 import 'memory_tests.dart';
 
 main(List<String> args) async {
   int length = args.length;
   if (length < 1) {
     print('Usage: dart benchmark_local.dart path_to_flutter_checkout'
         ' [benchmark_id]');
     return;
@@ skipping 188 matching lines @@
 
   PathHolder({String flutterPath}) {
     exampleHelloWorld = '$flutterPath/examples/hello_world';
     exampleGallery = '$flutterPath/examples/flutter_gallery';
     exampleStocks = '$flutterPath/examples/stocks';
     packageFlutter = '$flutterPath/packages/flutter';
     packageMarkdown = '$flutterPath/packages/flutter_markdown';
     packageSprites = '$flutterPath/packages/flutter_sprites';
   }
 }