Decide if unit without directives is a part or a library.

pkg/analysis_server/test/services/correction/fix_test.dart

Index: pkg/analysis_server/test/services/correction/fix_test.dart
diff --git a/pkg/analysis_server/test/services/correction/fix_test.dart b/pkg/analysis_server/test/services/correction/fix_test.dart
index 0778532d29f0745f9c1f7fd826ef893c2e1a6d77..4bbaeb1fb9e7e2c2e9db4dcebf1e6cc48abcb683 100644
--- a/pkg/analysis_server/test/services/correction/fix_test.dart
+++ b/pkg/analysis_server/test/services/correction/fix_test.dart
@@ -276,6 +276,7 @@ class A {}
 library my.lib;
 part 'part.dart';
 ''');
+    _performAnalysis();
     AnalysisError error = _findErrorToFix();
     fix = _assertHasFix(DartFixKind.ADD_PART_OF, error);
     change = fix.change;
@@ -3915,4 +3916,8 @@ main() {
     }
     return positions;
   }
+
+  void _performAnalysis() {
+    while (context.performAnalysisTask().hasMoreWork);
+  }
 }