Change HostResolver::Resolve() to take an std::unique_ptr<Request>* rather than a RequestHandle*

net/dns/single_request_host_resolver.cc

 // Copyright (c) 2011 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.
 
 #include "net/dns/single_request_host_resolver.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
 #include "net/base/net_errors.h"
 
 namespace net {
 
 SingleRequestHostResolver::SingleRequestHostResolver(HostResolver* resolver)
     : resolver_(resolver),
-      cur_request_(NULL),
       callback_(
           base::Bind(&SingleRequestHostResolver::OnResolveCompletion,
                      base::Unretained(this))) {
-  DCHECK(resolver_ != NULL);
+  DCHECK(resolver_ != nullptr);
 }
 
 SingleRequestHostResolver::~SingleRequestHostResolver() {
   Cancel();
 }
 
 int SingleRequestHostResolver::Resolve(const HostResolver::RequestInfo& info,
                                        RequestPriority priority,
                                        AddressList* addresses,
                                        const CompletionCallback& callback,
                                        const BoundNetLog& net_log) {
   DCHECK(addresses);
   DCHECK_EQ(false, callback.is_null());
   DCHECK(cur_request_callback_.is_null()) << "resolver already in use";
 
-  HostResolver::RequestHandle request = NULL;
+  std::unique_ptr<HostResolver::Request> request;
 
   // We need to be notified of completion before |callback| is called, so that
   // we can clear out |cur_request_*|.
   CompletionCallback transient_callback =
       callback.is_null() ? CompletionCallback() : callback_;
 
   int rv = resolver_->Resolve(
       info, priority, addresses, transient_callback, &request, net_log);
 
   if (rv == ERR_IO_PENDING) {
     DCHECK_EQ(false, callback.is_null());
     // Cleared in OnResolveCompletion().
-    cur_request_ = request;
+    cur_request_ = std::move(request);
     cur_request_callback_ = callback;
   }
 
   return rv;
 }
 
 void SingleRequestHostResolver::Cancel() {
   if (!cur_request_callback_.is_null()) {

[mmenke, 2016/07/19 19:03:56]

This check id no longer needed.  Clearing already empty objects is pretty
lightweight, and removing the condition marginally reduces code size.

[maksims (do not use this acc), 2016/07/21 07:12:46]

Done.

-    resolver_->CancelRequest(cur_request_);
-    cur_request_ = NULL;
+    cur_request_.reset();
     cur_request_callback_.Reset();
   }
 }
 
 void SingleRequestHostResolver::OnResolveCompletion(int result) {
   DCHECK(cur_request_);
   DCHECK_EQ(false, cur_request_callback_.is_null());
 
   CompletionCallback callback = cur_request_callback_;
 
   // Clear the outstanding request information.
-  cur_request_ = NULL;
+  cur_request_.reset();
   cur_request_callback_.Reset();
 
   // Call the user's original callback.
   callback.Run(result);
 }
 
 }  // namespace net