Fix VM implementation of CastError not to extend TypeError (issue 5280).

runtime/lib/error.h

Index: runtime/lib/error.h
===================================================================
--- runtime/lib/error.h	(revision 25753)
+++ runtime/lib/error.h	(working copy)
@@ -1,19 +0,0 @@
-// Copyright (c) 2011, 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.
-
-#ifndef LIB_ERROR_H_
-#define LIB_ERROR_H_
-
-#include "vm/runtime_entry.h"
-
-namespace dart {
-
-DECLARE_RUNTIME_ENTRY(ConditionTypeError);
-DECLARE_RUNTIME_ENTRY(MalformedTypeError);
-DECLARE_RUNTIME_ENTRY(TypeCheck);
-
-}  // namespace dart
-
-#endif  // LIB_ERROR_H_
-