[Autofill] Credit Card validation for rAc.

chrome/browser/autofill/validation.cc

 // Copyright (c) 2013 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.
 
 #include "chrome/browser/autofill/validation.h"
 
 #include "base/string_util.h"
 #include "chrome/browser/autofill/credit_card.h"
 
 namespace autofill {
@@ skipping 27 matching lines @@
       sum += digit / 10 + digit % 10;
     } else {
       sum += digit;
     }
     odd = !odd;
   }
 
   return (sum % 10) == 0;
 }
 
+bool IsValidCreditCardSecurityCode(const string16& text) {
+  if (text.size() < 3U || text.size() > 4U)
+    return false;
+
+  for (string16::const_iterator iter = text.begin();
+       iter != text.end();
+       ++iter) {
+    if (!IsAsciiDigit(*iter))
+      return false;
+  }
+  return true;
+}
+
 }  // namespace autofill