Make subclasses of AbstractContextTest asynchronous.

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

Index: pkg/analysis_server/test/services/refactoring/abstract_refactoring.dart
diff --git a/pkg/analysis_server/test/services/refactoring/abstract_refactoring.dart b/pkg/analysis_server/test/services/refactoring/abstract_refactoring.dart
index 793a1ec5dd4a1563bb91eac517a7c7494911e8dd..026c29f7219a24a4c2f628bb26f43c32b151bfe6 100644
--- a/pkg/analysis_server/test/services/refactoring/abstract_refactoring.dart
+++ b/pkg/analysis_server/test/services/refactoring/abstract_refactoring.dart
@@ -160,14 +160,14 @@ abstract class RefactoringTest extends AbstractSingleUnitTest {
         .resolveCompilationUnit(element.source, element.library);
   }
 
-  void indexTestUnit(String code) {
-    resolveTestUnit(code);
+  Future<Null> indexTestUnit(String code) async {
+    await resolveTestUnit(code);
     index.indexUnit(testUnit);
   }
 
-  void indexUnit(String file, String code) {
+  Future<Null> indexUnit(String file, String code) async {
     Source source = addSource(file, code);
-    CompilationUnit unit = resolveLibraryUnit(source);
+    CompilationUnit unit = await resolveLibraryUnit(source);
     index.indexUnit(unit);
   }