Implement CopyOnWriteBuffer move using scoped_refptr move

webrtc/base/copyonwritebuffer.cc

 /*
  *  Copyright 2016 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.
  */
 
 #include "webrtc/base/copyonwritebuffer.h"
 
 namespace rtc {
 
 CopyOnWriteBuffer::CopyOnWriteBuffer() {
   RTC_DCHECK(IsConsistent());
 }
 
 CopyOnWriteBuffer::CopyOnWriteBuffer(const CopyOnWriteBuffer& buf)
     : buffer_(buf.buffer_) {
 }
 
-CopyOnWriteBuffer::CopyOnWriteBuffer(CopyOnWriteBuffer&& buf) {
-  // TODO(jbauch): use std::move once scoped_refptr supports it (issue 5556)
-  std::swap(buffer_, buf.buffer_);
+CopyOnWriteBuffer::CopyOnWriteBuffer(CopyOnWriteBuffer&& buf)
+    : buffer_(std::move(buf.buffer_)) {
 }
 
 CopyOnWriteBuffer::CopyOnWriteBuffer(size_t size)
     : buffer_(size > 0 ? new RefCountedObject<Buffer>(size) : nullptr) {
   RTC_DCHECK(IsConsistent());
 }
 
 CopyOnWriteBuffer::CopyOnWriteBuffer(size_t size, size_t capacity)
     : buffer_(size > 0 || capacity > 0
           ? new RefCountedObject<Buffer>(size, capacity)
           : nullptr) {
   RTC_DCHECK(IsConsistent());
 }
 
 CopyOnWriteBuffer::~CopyOnWriteBuffer() = default;
 
 }  // namespace rtc