Reland Use CopyOnWriteBuffer instead of Buffer to avoid unnecessary copies.

webrtc/api/sctputils.h

 /*
  *  Copyright 2013 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_API_SCTPUTILS_H_
 #define WEBRTC_API_SCTPUTILS_H_
 
 #include <string>
 
 #include "webrtc/api/datachannelinterface.h"
 
 namespace rtc {
-class Buffer;
+class CopyOnWriteBuffer;
 }  // namespace rtc
 
 namespace webrtc {
 struct DataChannelInit;
 
 // Read the message type and return true if it's an OPEN message.
-bool IsOpenMessage(const rtc::Buffer& payload);
+bool IsOpenMessage(const rtc::CopyOnWriteBuffer& payload);
 
-bool ParseDataChannelOpenMessage(const rtc::Buffer& payload,
+bool ParseDataChannelOpenMessage(const rtc::CopyOnWriteBuffer& payload,
                                  std::string* label,
                                  DataChannelInit* config);
 
-bool ParseDataChannelOpenAckMessage(const rtc::Buffer& payload);
+bool ParseDataChannelOpenAckMessage(const rtc::CopyOnWriteBuffer& payload);
 
 bool WriteDataChannelOpenMessage(const std::string& label,
                                  const DataChannelInit& config,
-                                 rtc::Buffer* payload);
+                                 rtc::CopyOnWriteBuffer* payload);
 
-void WriteDataChannelOpenAckMessage(rtc::Buffer* payload);
+void WriteDataChannelOpenAckMessage(rtc::CopyOnWriteBuffer* payload);
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_SCTPUTILS_H_