Change analysis server protocol to omit empty lists when optional.

pkg/analysis_server/test/domain_server_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.domain.server;
 
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/domain_server.dart';
@@ skipping 35 matching lines @@
           SUBSCRIPTIONS: ['noSuchService']
         });
         var response = handler.handleRequest(request);
         expect(response, isResponseFailure('0'));
       });
 
       test('success', () {
         expect(server.serverServices, isEmpty);
         // send request
         Request request = new ServerSetSubscriptionsParams(
-            [ServerService.STATUS]).toRequest('0');
+            subscriptions: [ServerService.STATUS]).toRequest('0');
         var response = handler.handleRequest(request);
         expect(response, isResponseSuccess('0'));
         // set of services has been changed
         expect(server.serverServices, contains(ServerService.STATUS));
       });
     });
 
     test('shutdown', () {
       expect(server.running, isTrue);
       // send request
       var request = new Request('0', SERVER_SHUTDOWN);
       var response = handler.handleRequest(request);
       expect(response, isResponseSuccess('0'));
       // server is down
       expect(server.running, isFalse);
     });
   });
 }