Fix race condition with "server already started" error.

pkg/analysis_server/test/protocol_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.
 
 library test.protocol;
 
 import 'dart:convert';
 
 import 'package:analysis_server/src/protocol.dart';
 import 'package:unittest/unittest.dart';
@@ skipping 20 matching lines @@
     test('toJson', RequestTest.toJson);
     test('toJson_withParams', RequestTest.toJson_withParams);
   });
   group('RequestError', () {
     test('create', RequestErrorTest.create);
     test('create_methodNotFound', RequestErrorTest.create_methodNotFound);
     test('create_invalidParameters', RequestErrorTest.create_invalidParameters);
     test('create_invalidRequest', RequestErrorTest.create_invalidRequest);
     test('create_internalError', RequestErrorTest.create_internalError);
     test('create_parseError', RequestErrorTest.create_parseError);
+    test('create_serverAlreadyStarted',
+        RequestErrorTest.create_serverAlreadyStarted);
     test('fromJson', RequestErrorTest.fromJson);
     test('toJson', RequestErrorTest.toJson);
   });
   group('Response', () {
     test('create_contextDoesNotExist', ResponseTest.create_contextDoesNotExist);
     test('create_invalidRequestFormat', ResponseTest.create_invalidRequestFormat);
     test('create_missingRequiredParameter', ResponseTest.create_missingRequiredParameter);
     test('create_unknownAnalysisOption', ResponseTest.create_unknownAnalysisOption);
     test('create_unknownRequest', ResponseTest.create_unknownRequest);
     test('setResult', ResponseTest.setResult);
@@ skipping 180 matching lines @@
     expect(error.code, RequestError.CODE_INVALID_REQUEST);
     expect(error.message, "Invalid request");
   }
 
   static void create_internalError() {
     RequestError error = new RequestError.internalError();
     expect(error.code, RequestError.CODE_INTERNAL_ERROR);
     expect(error.message, "Internal error");
   }
 
+  static void create_serverAlreadyStarted() {
+    RequestError error = new RequestError.serverAlreadyStarted();
+    expect(error.code, RequestError.CODE_SERVER_ALREADY_STARTED);
+    expect(error.message, "Server already started");
+  }
+
   static void fromJson() {
     var json = {
         RequestError.CODE: RequestError.CODE_PARSE_ERROR,
         RequestError.MESSAGE: 'foo',
         RequestError.DATA: {'ints': [1, 2, 3]}
     };
     RequestError error = new RequestError.fromJson(json);
     expect(error.code, RequestError.CODE_PARSE_ERROR);
     expect(error.message, "foo");
     expect(error.data['ints'], [1, 2, 3]);
@@ skipping 99 matching lines @@
     original.setResult('foo', 'bar');
     Response response = new Response.fromJson(original.toJson());
     expect(response.id, equals('myId'));
     Map<String, Object> result = response.result;
     expect(result.length, equals(1));
     expect(result['foo'], equals('bar'));
   }
 }
 
 Matcher _throwsRequestFailure = throwsA(new isInstanceOf<RequestFailure>());