Add move support for scoped_refptr.

base/memory/ref_counted.h

Index: base/memory/ref_counted.h
diff --git a/base/memory/ref_counted.h b/base/memory/ref_counted.h
index 219437ed8d82b8b35835a6c3297d5f719f14c277..7320dee6779daf5dfe8248faac04d0748234ee92 100644
--- a/base/memory/ref_counted.h
+++ b/base/memory/ref_counted.h
@@ -14,6 +14,7 @@
 #ifndef NDEBUG
 #include "base/logging.h"
 #endif
+#include "base/move.h"
 #include "base/threading/thread_collision_warner.h"
 #include "build/build_config.h"
 
@@ -264,6 +265,7 @@ class RefCountedData
 //
 template <class T>
 class scoped_refptr {
+  TYPE_WITH_MOVE_CONSTRUCTOR_FOR_CPP_03(scoped_refptr)
  public:
   typedef T element_type;
 
@@ -286,6 +288,11 @@ class scoped_refptr {
       AddRef(ptr_);
   }
 
+  template <typename U>
+  scoped_refptr(scoped_refptr<U>&& r) : ptr_(r.get()) {
+    r.ptr_ = nullptr;
+  }
+
   ~scoped_refptr() {
     if (ptr_)
       Release(ptr_);
@@ -323,6 +330,12 @@ class scoped_refptr {
     return *this = r.get();
   }
 
+  template <typename U>
+  scoped_refptr<T>& operator=(scoped_refptr<U>&& r) {
+    scoped_refptr<T>(r.Pass()).swap(*this);

[danakj, 2015/04/10 19:44:24]

This is:
temp.ptr_ = r.ptr_;
r.ptr_ = nullptr;
T* p = ptr_;
ptr_ = temp.ptr_;
temp.ptr_ = p;

You could do this as:
T* p = r.ptr_;
r.ptr_ = nullptr;
ptr_ = p;

And get the same thing?

[Kibeom Kim (inactive), 2015/04/12 07:35:14]

Yeah you're right. it also needs |if (ptr_) Release(ptr_);| to be identical.
(corresponds to the temp destructor)

T* p = r.get();
r.ptr_ = nullptr;
if (ptr_)
  Release(ptr_);
ptr_ = p;

+    return *this;
+  }
+
   void swap(T** pp) {
     T* p = ptr_;
     ptr_ = *pp;
@@ -334,6 +347,8 @@ class scoped_refptr {
   }
 
  private:
+  template <typename U> friend class scoped_refptr;
+
   // Allow scoped_refptr<T> to be used in boolean expressions, but not
   // implicitly convertible to a real bool (which is dangerous).
   //