Added back helper file accidentally deleted during test block 219 migration.

tests/lib/mirrors/deferred_mirrors_update_test.dart

Index: tests/lib/mirrors/deferred_mirrors_update_test.dart
diff --git a/tests/lib/mirrors/deferred_mirrors_update_test.dart b/tests/lib/mirrors/deferred_mirrors_update_test.dart
deleted file mode 100644
index 74c76d41340579682c42c7d65b92fbce7213bab4..0000000000000000000000000000000000000000
--- a/tests/lib/mirrors/deferred_mirrors_update_test.dart
+++ /dev/null
@@ -1,17 +0,0 @@
-library main;
-
-// Test that the library-mirrors are updated after loading a deferred library.
-
-@MirrorsUsed(targets: "D")
-import "dart:mirrors";
-
-import "deferred_mirrors_update_lib.dart" deferred as l;
-
-class D {}
-
-void main() {
-  print(reflectClass(D).owner);
-  l.loadLibrary().then((_) {
-    l.foo();
-  });
-}