Update documentation for base::ResetAndReturn(Callback*)

base/callback_helpers.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This defines helpful methods for dealing with Callbacks.  Because Callbacks
 // are implemented using templates, with a class per callback signature, adding
 // methods to Callback<> itself is unattractive (lots of extra code gets
 // generated).  Instead, consider adding methods here.
 //
 // ResetAndReturn(&cb) is like cb.Reset() but allows executing a callback (via a
-// copy) after the original callback is Reset().  This can be handy if Run()
-// reads/writes the variable holding the Callback.
+// move or copy) after the original callback is Reset().  This can be handy if

[michaelpg, 2017/03/17 03:55:00]

I think it's normally a move, since its return value will be treated as an
rvalue reference to a temporary (or elided); if it was always a copy, it
wouldn't work with OnceCallback.

+// Run() reads/writes the variable holding the Callback.
 
 #ifndef BASE_CALLBACK_HELPERS_H_
 #define BASE_CALLBACK_HELPERS_H_
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 
 namespace base {
 
@@ skipping 32 matching lines @@
 
  private:
   Closure closure_;
 
   DISALLOW_COPY_AND_ASSIGN(ScopedClosureRunner);
 };
 
 }  // namespace base
 
 #endif  // BASE_CALLBACK_HELPERS_H_