Reland of place string::find(prefix) == 0 pattern with base::StartsWith().

components/os_crypt/os_crypt_posix.cc

 // Copyright 2014 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 "components/os_crypt/os_crypt.h"
 
 #include <stddef.h>
 
 #include <memory>
 
 #include "base/logging.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "crypto/encryptor.h"
 #include "crypto/symmetric_key.h"
 
 namespace {
 
 // Salt for Symmetric key derivation.
 const char kSalt[] = "saltysalt";
 
 // Key size required for 128 bit AES.
@@ skipping 89 matching lines @@
   if (ciphertext.empty()) {
     *plaintext = std::string();
     return true;
   }
 
   // Check that the incoming cyphertext was indeed encrypted with the expected
   // version.  If the prefix is not found then we'll assume we're dealing with
   // old data saved as clear text and we'll return it directly.
   // Credit card numbers are current legacy data, so false match with prefix
   // won't happen.
-  if (ciphertext.find(kObfuscationPrefix) != 0) {
+  if (!base::StartsWith(ciphertext, kObfuscationPrefix,
+                        base::CompareCase::SENSITIVE)) {
     *plaintext = ciphertext;
     return true;
   }
 
   // Strip off the versioning prefix before decrypting.
   std::string raw_ciphertext = ciphertext.substr(strlen(kObfuscationPrefix));
 
   std::unique_ptr<crypto::SymmetricKey> encryption_key(GetEncryptionKey());
   if (!encryption_key.get())
     return false;
 
   std::string iv(kIVBlockSizeAES128, ' ');
   crypto::Encryptor encryptor;
   if (!encryptor.Init(encryption_key.get(), crypto::Encryptor::CBC, iv))
     return false;
 
   if (!encryptor.Decrypt(raw_ciphertext, plaintext))
     return false;
 
   return true;
 }