Move the wire protocol support into the public API

pkg/analysis_server/test/integration/analysis/highlights_test2.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.
 
 library test.integration.analysis.highlights2;
 
 import 'dart:async';
 
-import 'package:analysis_server/src/protocol.dart';
+import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../utils.dart';
 import '../integration_tests.dart';
 
 main() {
   initializeTestEnvironment();
   defineReflectiveTests(AnalysisHighlightsTest);
 }
@@ skipping 127 matching lines @@
       check(HighlightRegionType.INSTANCE_SETTER_DECLARATION, ['setter']);
       check(HighlightRegionType.TOP_LEVEL_GETTER_REFERENCE, ['override']);
       check(HighlightRegionType.TOP_LEVEL_VARIABLE_DECLARATION,
           ['topLevelVariable']);
       check(HighlightRegionType.TYPE_NAME_DYNAMIC, ['dynamic']);
       check(HighlightRegionType.TYPE_PARAMETER, ['TypeParameter']);
       expect(highlights, isEmpty);
     });
   }
 }