A follow-up of r64178....

net/base/ssl_connection_status_flags.h

 // Copyright (c) 2010 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 NET_BASE_SSL_CONNECTION_STATUS_FLAGS_H_
 #define NET_BASE_SSL_CONNECTION_STATUS_FLAGS_H_
 #pragma once
 
 namespace net {
 
@@ skipping 12 matching lines @@
 
   // The server doesn't support the renegotiation_info extension. If this bit
   // is not set then either the extension isn't supported, or we don't have any
   // knowledge either way. (The latter case will occur when we use an SSL
   // library that doesn't report it, like SChannel.)
   SSL_CONNECTION_NO_RENEGOTIATION_EXTENSION = 1 << 19,
 
   // The next three bits are reserved for the SSL version.
   SSL_CONNECTION_VERSION_SHIFT = 20,
   SSL_CONNECTION_VERSION_MASK = 7,
-  SSL_CONNECTION_VERSION_UNKNOWN = 0,  // Unknown SSL version or SSL not used.
+
+  // 1 << 31 (the sign bit) is reserved so that the SSL connection status will
+  // never be negative.
+};
+
+// NOTE: the SSL version enum constants must be between 0 and
+// SSL_CONNECTION_VERSION_MASK, inclusive.
+enum {
+  SSL_CONNECTION_VERSION_UNKNOWN = 0,  // Unknown SSL version.
   SSL_CONNECTION_VERSION_SSL2 = 1,
   SSL_CONNECTION_VERSION_SSL3 = 2,
   SSL_CONNECTION_VERSION_TLS1 = 3,
   SSL_CONNECTION_VERSION_TLS1_1 = 4,
   SSL_CONNECTION_VERSION_TLS1_2 = 5,
-
-  // 1 << 31 (the sign bit) is reserved so that the SSL connection status will
-  // never be negative.
+  SSL_CONNECTION_VERSION_MAX,
 };
+COMPILE_ASSERT(SSL_CONNECTION_VERSION_MAX - 1 <= SSL_CONNECTION_VERSION_MASK,
+               SSL_CONNECTION_VERSION_MASK_too_small);
 
 inline int SSLConnectionStatusToCipherSuite(int connection_status) {
   return (connection_status >> SSL_CONNECTION_CIPHERSUITE_SHIFT) &
          SSL_CONNECTION_CIPHERSUITE_MASK;
 }
 
 inline int SSLConnectionStatusToCompression(int connection_status) {
   return (connection_status >> SSL_CONNECTION_COMPRESSION_SHIFT) &
          SSL_CONNECTION_COMPRESSION_MASK;
 }
 
 inline int SSLConnectionStatusToVersion(int connection_status) {
   return (connection_status >> SSL_CONNECTION_VERSION_SHIFT) &
          SSL_CONNECTION_VERSION_MASK;
 }
 
 }  // namespace net
 
 #endif  // NET_BASE_SSL_CONNECTION_STATUS_FLAGS_H_