MD5Update function uses StringPiece instead of raw buffer.

base/md5.h

 // Copyright (c) 2011 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_MD5_H_
 #define BASE_MD5_H_
 #pragma once
 
-#include <string>
-
 #include "base/base_api.h"
+#include "base/string_piece.h"
 
 namespace base {
 
 // MD5 stands for Message Digest algorithm 5.
 // MD5 is a robust hash function, designed for cyptography, but often used
 // for file checksums.  The code is complex and slow, but has few
 // collisions.
 // See Also:
 //   http://en.wikipedia.org/wiki/MD5
 
@@ skipping 23 matching lines @@
 typedef char MD5Context[88];
 
 // Computes the MD5 sum of the given data buffer with the given length.
 // The given 'digest' structure will be filled with the result data.
 BASE_API void MD5Sum(const void* data, size_t length, MD5Digest* digest);
 
 // Initializes the given MD5 context structure for subsequent calls to
 // MD5Update().
 BASE_API void MD5Init(MD5Context* context);
 
-// For the given buffer of data, updates the given MD5 context with the sum of
-// the data. You can call this any number of times during the computation,
-// except that MD5Init() must have been called first.
-BASE_API void MD5Update(MD5Context* context, const void* data, size_t length);
+// For the given buffer of |data| as a StringPiece, updates the given MD5
+// context with the sum of the data. You can call this any number of times
+// during the computation, except that MD5Init() must have been called first.
+BASE_API void MD5Update(MD5Context* context, const StringPiece& data);
 
 // Finalizes the MD5 operation and fills the buffer with the digest.
 BASE_API void MD5Final(MD5Digest* digest, MD5Context* context);
 
 // Converts a digest into human-readable hexadecimal.
 BASE_API std::string MD5DigestToBase16(const MD5Digest& digest);
 
 // Returns the MD5 (in hexadecimal) of a string.
-BASE_API std::string MD5String(const std::string& str);
+BASE_API std::string MD5String(const StringPiece& str);
 
 }  // namespace base
 
 // TODO(tfarina): Fix third_party/hunspell then remove this hack.
 using base::MD5Digest;
 
 #endif  // BASE_MD5_H_