Use different SDKs based on option settings

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:analysis_server/plugin/protocol/protocol.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 19 matching lines @@
     ExtensionManager manager = new ExtensionManager();
     ServerPlugin serverPlugin = new ServerPlugin();
     manager.processPlugins([serverPlugin]);
     server = new AnalysisServer(
         serverChannel,
         resourceProvider,
         new MockPackageMapProvider(),
         null,
         serverPlugin,
         new AnalysisServerOptions(),
-        new MockSdk(),
+        () => new MockSdk(),
         InstrumentationService.NULL_SERVICE);
     handler = new ServerDomainHandler(server);
   });
 
   group('ServerDomainHandler', () {
     test('getVersion', () {
       var request = new ServerGetVersionParams().toRequest('0');
       var response = handler.handleRequest(request);
       expect(
           response.toJson(),
@@ skipping 29 matching lines @@
       expect(server.running, isTrue);
       // send request
       var request = new ServerShutdownParams().toRequest('0');
       var response = handler.handleRequest(request);
       expect(response, isResponseSuccess('0'));
       // server is down
       expect(server.running, isFalse);
     });
   });
 }