Do not hide membership of implementation classes in dart:core.

tests/lib/mirrors/hierarchy_invariants_test.dart

Index: tests/lib/mirrors/hierarchy_invariants_test.dart
diff --git a/tests/lib/mirrors/hierarchy_invariants_test.dart b/tests/lib/mirrors/hierarchy_invariants_test.dart
index 0197dd3805b25452a1888e348f658cb1ad7d44b9..19d3152a0ac77d2c6e2ca1f3fe9cf8600e551742 100644
--- a/tests/lib/mirrors/hierarchy_invariants_test.dart
+++ b/tests/lib/mirrors/hierarchy_invariants_test.dart
@@ -8,12 +8,22 @@ import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
+isAnonymousMixinApplication(classMirror) {
+  return MirrorSystem.getName(classMirror.simpleName).contains(' with ');
+}
+
 check(classMirror) {
   if (classMirror is TypedefMirror) return;
 
   Expect.isTrue(classMirror.simpleName is Symbol);
   Expect.notEquals(null, classMirror.owner);
   Expect.isTrue(classMirror.owner is LibraryMirror);
+  if (!isAnonymousMixinApplication(classMirror)) {
+    Expect.equals(classMirror.originalDeclaration,
+                  classMirror.owner.classes[classMirror.simpleName]);
+  } else {
+    Expect.isNull(classMirror.owner.classes[classMirror.simpleName]);
+  }
   Expect.isTrue(classMirror.superinterfaces is List);
   if (classMirror.superclass == null) {
     Expect.equals(reflectClass(Object), classMirror);