Clean-up the registration of plugins

pkg/analysis_server/test/domain_completion_test.dart

Index: pkg/analysis_server/test/domain_completion_test.dart
diff --git a/pkg/analysis_server/test/domain_completion_test.dart b/pkg/analysis_server/test/domain_completion_test.dart
index 625174ebdbb9b24af1361adac0a7855c5b083476..c57102297e7903ee7c6e38f2f406d9a2a365e530 100644
--- a/pkg/analysis_server/test/domain_completion_test.dart
+++ b/pkg/analysis_server/test/domain_completion_test.dart
@@ -29,6 +29,7 @@ import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:plugin/manager.dart';
+import 'package:plugin/plugin.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
@@ -56,9 +57,22 @@ class CompletionManagerTest extends AbstractAnalysisTest {
   bool wasTaskModelEnabled;
 
   AnalysisServer createAnalysisServer(Index index) {
-    ExtensionManager manager = new ExtensionManager();
+    //
+    // Collect plugins
+    //
     ServerPlugin serverPlugin = new ServerPlugin();
-    manager.processPlugins([serverPlugin]);
+    List<Plugin> plugins = <Plugin>[];
+    plugins.addAll(AnalysisEngine.instance.requiredPlugins);
+    plugins.add(serverPlugin);
+    addServerPlugins(plugins);
+    //
+    // Process plugins
+    //
+    ExtensionManager manager = new ExtensionManager();
+    manager.processPlugins(plugins);
+    //
+    // Create the server
+    //
     return new Test_AnalysisServer(
         super.serverChannel,
         super.resourceProvider,