Reland Use CopyOnWriteBuffer instead of Buffer to avoid unnecessary copies.

webrtc/base/sslfingerprint.h

 /*
  *  Copyright 2012 The WebRTC Project Authors. All rights reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_BASE_SSLFINGERPRINT_H_
 #define WEBRTC_BASE_SSLFINGERPRINT_H_
 
 #include <string>
 
 #include "webrtc/base/basictypes.h"
-#include "webrtc/base/buffer.h"
+#include "webrtc/base/copyonwritebuffer.h"
 #include "webrtc/base/sslidentity.h"
 
 namespace rtc {
 
 class SSLCertificate;
 
 struct SSLFingerprint {
   static SSLFingerprint* Create(const std::string& algorithm,
                                 const rtc::SSLIdentity* identity);
 
   static SSLFingerprint* Create(const std::string& algorithm,
                                 const rtc::SSLCertificate* cert);
 
   static SSLFingerprint* CreateFromRfc4572(const std::string& algorithm,
                                            const std::string& fingerprint);
 
   SSLFingerprint(const std::string& algorithm,
                  const uint8_t* digest_in,
                  size_t digest_len);
 
   SSLFingerprint(const SSLFingerprint& from);
 
   bool operator==(const SSLFingerprint& other) const;
 
   std::string GetRfc4572Fingerprint() const;
 
   std::string ToString();
 
   std::string algorithm;
-  rtc::Buffer digest;
+  rtc::CopyOnWriteBuffer digest;
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_SSLFINGERPRINT_H_