Add a Dns preresolve interface in //content

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 "base/memory/ptr_util.h"
+#include "net/base/address_list.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))) {
+      callback_(base::Bind(&SingleRequestHostResolver::OnResolveCompletion,
+                           base::Unretained(this))),
+      default_addresses_(nullptr) {
   DCHECK(resolver_ != NULL);
 }
 
 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";
 
+  if (!addresses) {
+    default_addresses_ = base::WrapUnique(new AddressList);
+    addresses = default_addresses_.get();
+  }
+
   HostResolver::RequestHandle request = NULL;
 
   // 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);
 
@@ skipping 23 matching lines @@
 
   // Clear the outstanding request information.
   cur_request_ = NULL;
   cur_request_callback_.Reset();
 
   // Call the user's original callback.
   callback.Run(result);
 }
 
 }  // namespace net