[refactor] Replace custom utility function with base's "vector_as_array()"

content/child/webcrypto/webcrypto_util.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 "content/child/webcrypto/webcrypto_util.h"
 
 #include "base/base64.h"
 #include "base/logging.h"
+#include "base/stl_util.h"
 #include "base/strings/stringprintf.h"
 #include "content/child/webcrypto/status.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithm.h"
 #include "third_party/WebKit/public/platform/WebCryptoAlgorithmParams.h"
 #include "third_party/WebKit/public/platform/WebCryptoKeyAlgorithm.h"
 
 namespace content {
 
 namespace webcrypto {
 
-const uint8_t* Uint8VectorStart(const std::vector<uint8_t>& data) {
-  if (data.empty())
-    return NULL;
-  return &data[0];
-}
-
-uint8_t* Uint8VectorStart(std::vector<uint8_t>* data) {
-  if (data->empty())
-    return NULL;
-  return &(*data)[0];
-}
-
 // This function decodes unpadded 'base64url' encoded data, as described in
 // RFC4648 (http://www.ietf.org/rfc/rfc4648.txt) Section 5. To do this, first
 // change the incoming data to 'base64' encoding by applying the appropriate
 // transformation including adding padding if required, and then call a base64
 // decoder.
 bool Base64DecodeUrlSafe(const std::string& input, std::string* output) {
   std::string base64EncodedText(input);
   std::replace(base64EncodedText.begin(), base64EncodedText.end(), '-', '+');
   std::replace(base64EncodedText.begin(), base64EncodedText.end(), '_', '/');
   base64EncodedText.append((4 - base64EncodedText.size() % 4) % 4, '=');
   return base::Base64Decode(base64EncodedText, output);
 }
 
 // Returns an unpadded 'base64url' encoding of the input data, using the
 // inverse of the process above.
 std::string Base64EncodeUrlSafe(const base::StringPiece& input) {
   std::string output;
   base::Base64Encode(input, &output);
   std::replace(output.begin(), output.end(), '+', '-');
   std::replace(output.begin(), output.end(), '/', '_');
   output.erase(std::remove(output.begin(), output.end(), '='), output.end());
   return output;
 }
 
 std::string Base64EncodeUrlSafe(const std::vector<uint8_t>& input) {
   const base::StringPiece string_piece(
-      reinterpret_cast<const char*>(Uint8VectorStart(input)), input.size());
+      reinterpret_cast<const char*>(vector_as_array(&input)), input.size());
   return Base64EncodeUrlSafe(string_piece);
 }
 
 struct JwkToWebCryptoUsage {
   const char* const jwk_key_op;
   const blink::WebCryptoKeyUsage webcrypto_usage;
 };
 
 // Keep this ordered according to the definition
 // order of WebCrypto's "recognized key usage
@@ skipping 188 matching lines @@
 Status CheckKeyCreationUsages(blink::WebCryptoKeyUsageMask all_possible_usages,
                               blink::WebCryptoKeyUsageMask actual_usages) {
   if (!ContainsKeyUsages(all_possible_usages, actual_usages))
     return Status::ErrorCreateKeyBadUsages();
   return Status::Success();
 }
 
 }  // namespace webcrypto
 
 }  // namespace content