Make TypedefMirror a direct descendant of TypeMirror.

runtime/tests/vm/dart/isolate_mirror_local_test.dart

 // Copyright (c) 2012, 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.
 //
 // Dart test program for checking implemention of MirrorSystem when
 // inspecting the current isolate.
 //
 // VMOptions=--enable_type_checks
 
 library isolate_mirror_local_test;
@@ skipping 152 matching lines @@
                 'testMirrorErrors, '
                 'testMirrorSystem, '
                 'testNullInstanceMirror, '
                 'testRootLibraryMirror, '
                 'testStringInstanceMirror]',
                 '$keys');
 
   // Check that the classes map is complete.
   keys = lib_mirror.classes.keys.map(MirrorSystem.getName).toList();
   sort(keys);
+  print(keys);
+  Expect.equals('['
+                'GenericClass, '
+                'MyClass, '
+                'MyException, '
+                'MyInterface, '
+                'MySuperClass]',
+                '$keys');
+
+  // Check that the types map is complete.
+  keys = lib_mirror.types.keys.map(MirrorSystem.getName).toList();
+  sort(keys);
+  print(keys);
   Expect.equals('['
                 'FuncType, '
                 'GenericClass, '
                 'MyClass, '
                 'MyException, '
                 'MyInterface, '
                 'MySuperClass]',
                 '$keys');
 
   // Check that the functions map is complete.
@@ skipping 351 matching lines @@
   // Test that an isolate can reflect on itself.
   mirrorSystemOf(exit_port.toSendPort()).then(testMirrorSystem);
 
   testIntegerInstanceMirror(reflect(1001));
   testStringInstanceMirror(reflect('This\nis\na\nString'));
   testBoolInstanceMirror(reflect(true));
   testNullInstanceMirror(reflect(null));
   testCustomInstanceMirror(reflect(new MyClass(17)));
   testMirrorErrors(currentMirrorSystem());
 }