Make pubspec.lock keep relative path if it is originally specified as relative in pubspec.yaml (iss…

sdk/lib/_internal/pub/test/test_pub.dart

Index: sdk/lib/_internal/pub/test/test_pub.dart
diff --git a/sdk/lib/_internal/pub/test/test_pub.dart b/sdk/lib/_internal/pub/test/test_pub.dart
index 5da6eb62a3931ad7435b5e88d96068faea8fda38..33ea60ea3e196e3de03ff42eba03622836a17166 100644
--- a/sdk/lib/_internal/pub/test/test_pub.dart
+++ b/sdk/lib/_internal/pub/test/test_pub.dart
@@ -32,6 +32,8 @@ import '../lib/src/lock_file.dart';
 import '../lib/src/log.dart' as log;
 import '../lib/src/package.dart';
 import '../lib/src/safe_http_server.dart';
+import '../lib/src/source/path.dart';
+import '../lib/src/source_registry.dart';
 import '../lib/src/system_cache.dart';
 import '../lib/src/utils.dart';
 import '../lib/src/validator.dart';
@@ -653,7 +655,12 @@ void createLockFile(String package, {Iterable<String> sandbox,
     });
     lockFile.packages[name] = id;
   });
-  d.file(path.join(package, 'pubspec.lock'), lockFile.serialize()).create();
+
+  var sources = new SourceRegistry()
+    ..register(new PathSource());
+
+  d.file(path.join(package, 'pubspec.lock'),
+      lockFile.serialize(null, sources)).create();
 }
 
 /// Use [client] as the mock HTTP client for this test.