Fix test failures on the bots

pkg/analysis_server/test/services/completion/optype_test.dart

Index: pkg/analysis_server/test/services/completion/optype_test.dart
diff --git a/pkg/analysis_server/test/services/completion/optype_test.dart b/pkg/analysis_server/test/services/completion/optype_test.dart
index 94b5dafe2c1cc204d83cb2a7038d7ac0f2e8f566..8f9880b815aad61f0ac8e1d80adf33ed8a3bcb6d 100644
--- a/pkg/analysis_server/test/services/completion/optype_test.dart
+++ b/pkg/analysis_server/test/services/completion/optype_test.dart
@@ -9,6 +9,7 @@ import 'package:analysis_server/src/services/completion/optype.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
+import 'package:plugin/manager.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
@@ -67,6 +68,11 @@ class OpTypeTest {
     expect(visitor.isPrefixed, prefixed, reason: 'prefixed');
   }
 
+  void setUp() {
+    ExtensionManager extensionManager = new ExtensionManager();
+    extensionManager.processPlugins(AnalysisEngine.instance.supportedPlugins);
+  }
+
   test_Annotation() {
     // SimpleIdentifier  Annotation  MethodDeclaration  ClassDeclaration
     addTestSource('class C { @A^ }');