Update pub to use the new command runner API in args.

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

Index: sdk/lib/_internal/pub_generated/test/test_pub.dart
diff --git a/sdk/lib/_internal/pub_generated/test/test_pub.dart b/sdk/lib/_internal/pub_generated/test/test_pub.dart
index 72ee6a04d5153e75366555ff1a5093cfb3c70e4a..1fcc8d67aece400ab78239f1327d36679220200b 100644
--- a/sdk/lib/_internal/pub_generated/test/test_pub.dart
+++ b/sdk/lib/_internal/pub_generated/test/test_pub.dart
@@ -978,7 +978,8 @@ typedef Validator ValidatorCreator(Entrypoint entrypoint);
 Future<Pair<List<String>, List<String>>>
     schedulePackageValidation(ValidatorCreator fn) {
   return schedule(() {
-    var cache = new SystemCache.withSources(p.join(sandboxDir, cachePath));
+    var cache =
+        new SystemCache.withSources(rootDir: p.join(sandboxDir, cachePath));
 
     return new Future.sync(() {
       var validator = fn(new Entrypoint(p.join(sandboxDir, appPath), cache));