Pull in test_reflective_loader 0.0.4 and switch analyzer to it.

pkg/analyzer/test/source/package_map_resolver_test.dart

Index: pkg/analyzer/test/source/package_map_resolver_test.dart
diff --git a/pkg/analyzer/test/source/package_map_resolver_test.dart b/pkg/analyzer/test/source/package_map_resolver_test.dart
index 745350573524a162c4a52b30474bdad4933803be..7cdcabc4430fa9407e9239fe3d6d034eca2d3251 100644
--- a/pkg/analyzer/test/source/package_map_resolver_test.dart
+++ b/pkg/analyzer/test/source/package_map_resolver_test.dart
@@ -9,14 +9,14 @@ import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:path/path.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
 import 'package:unittest/unittest.dart';
 
-import '../reflective_tests.dart';
 import '../utils.dart';
 
 main() {
   initializeTestEnvironment();
-  runReflectiveTests(_PackageMapUriResolverTest);
+  defineReflectiveTests(_PackageMapUriResolverTest);
 }
 
 @reflectiveTest