Implement patch records to patch canonical objects.

tests/language/issue21079_test.dart

Index: tests/language/issue21079_test.dart
diff --git a/tests/language/issue21079_test.dart b/tests/language/issue21079_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f0af3f5c97e625ac03e0e08dcfc23574b971af2d
--- /dev/null
+++ b/tests/language/issue21079_test.dart
@@ -0,0 +1,18 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Regression test case for http://dartbug.com/21079
+import 'dart:mirrors';
+import 'dart:isolate';
+import "package:expect/expect.dart";
+
+void main() {
+  Expect.isTrue(reflectClass(MyException).superclass.reflectedType == IsolateSpawnException);
+
+  Expect.isTrue(reflectClass(IsolateSpawnException).reflectedType == IsolateSpawnException);
+}
+
+class MyException extends IsolateSpawnException {}
+
+