Implement off-the-wire validation scheme for enum types.

base/enum_validation.h

Index: base/enum_validation.h
diff --git a/base/enum_validation.h b/base/enum_validation.h
new file mode 100644
index 0000000000000000000000000000000000000000..4d4e3f30e76a73bff899d902b2f0352b8275ebee
--- /dev/null
+++ b/base/enum_validation.h
@@ -0,0 +1,13 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_ENUM_VALIDATION_H
+#define BASE_ENUM_VALIDATION_H
+
+// Defines a function template which enum authors can specialize to perform
+// validation upon an untrusted value prior to its being cast to their enum
+// type. Intended mainly for use by (generated) unmarshalling code.
+template <typename T> inline bool IsIntValidForEnum(int x) { return true; }
+
+#endif // BASE_ENUM_VALIDATION_H