Make subclasses of AbstractContextTest asynchronous.

pkg/analysis_server/test/services/refactoring/rename_label_test.dart

Index: pkg/analysis_server/test/services/refactoring/rename_label_test.dart
diff --git a/pkg/analysis_server/test/services/refactoring/rename_label_test.dart b/pkg/analysis_server/test/services/refactoring/rename_label_test.dart
index c1e995f5a51f5b8c8d4880800cfbe35cfa32d39c..64345a2e2bfb001993af852ced49ee2471397255 100644
--- a/pkg/analysis_server/test/services/refactoring/rename_label_test.dart
+++ b/pkg/analysis_server/test/services/refactoring/rename_label_test.dart
@@ -18,8 +18,8 @@ main() {
 
 @reflectiveTest
 class RenameLabelTest extends RenameRefactoringTest {
-  test_checkNewName_LocalVariableElement() {
-    indexTestUnit('''
+  test_checkNewName_LocalVariableElement() async {
+    await indexTestUnit('''
 main() {
 test:
   while (true) {
@@ -43,8 +43,8 @@ test:
     assertRefactoringStatusOK(refactoring.checkNewName());
   }
 
-  test_createChange() {
-    indexTestUnit('''
+  test_createChange() async {
+    await indexTestUnit('''
 main() {
 test:
   while (true) {
@@ -68,8 +68,8 @@ newName:
 ''');
   }
 
-  test_oldName() {
-    indexTestUnit('''
+  test_oldName() async {
+    await indexTestUnit('''
 main() {
 test:
   while (true) {