Adds move assignment operator to scoped_refptr

webrtc/base/scoped_ref_ptr.h

 /*
  *  Copyright 2011 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.
  */
 
@@ skipping 45 matching lines @@
 //     scoped_refptr<MyFoo> b;
 //
 //     b = a;
 //     // now, |a| and |b| each own a reference to the same MyFoo object.
 //   }
 //
 
 #ifndef WEBRTC_BASE_SCOPED_REF_PTR_H_
 #define WEBRTC_BASE_SCOPED_REF_PTR_H_
 
-#include <stddef.h>
+#include <memory>
 
 namespace rtc {
 
 template <class T>
 class scoped_refptr {
  public:
   scoped_refptr() : ptr_(NULL) {
   }
 
   scoped_refptr(T* p) : ptr_(p) {
@@ skipping 50 matching lines @@
 
   scoped_refptr<T>& operator=(const scoped_refptr<T>& r) {
     return *this = r.ptr_;
   }
 
   template <typename U>
   scoped_refptr<T>& operator=(const scoped_refptr<U>& r) {
     return *this = r.get();
   }
 
+  scoped_refptr<T>& operator=(scoped_refptr<T>&& r) {
+    scoped_refptr<T>(std::move(r)).swap(*this);

[Taylor Brandstetter, 2016/08/01 20:00:36]

I realize this uses the same method as Chromium's scoped_refptr, but do you know
why the std::move is used? Isn't `r` already movable, and so isn't this
std::move a no-op?

+    return *this;
+  }
+
+  template <typename U>
+  scoped_refptr<T>& operator=(scoped_refptr<U>&& r) {
+    scoped_refptr<T>(std::move(r)).swap(*this);
+    return *this;
+  }
+
   void swap(T** pp) {
     T* p = ptr_;
     ptr_ = *pp;
     *pp = p;
   }
 
   void swap(scoped_refptr<T>& r) {
     swap(&r.ptr_);
   }
 
  protected:
   T* ptr_;
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_SCOPED_REF_PTR_H_