Add a Dns preresolve interface in //content

content/browser/loader/resource_hints_impl.h

+// Copyright 2016 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.
+
+#ifndef CONTENT_BROWSER_LOADER_RESOURCE_HINTS_IMPL_H_
+#define CONTENT_BROWSER_LOADER_RESOURCE_HINTS_IMPL_H_
+
+#include <set>
+
+#include "base/macros.h"
+#include "net/base/address_list.h"
+#include "net/dns/host_resolver.h"
+#include "net/dns/single_request_host_resolver.h"
+#include "net/url_request/url_request_context_getter.h"
+
+namespace content {
+
+// Scoped to the ResourceDispatcherHostImpl.

[Charlie Harrison, 2016/05/20 16:30:26]

I've added a more detailed comment here in the next patch.

+class ResourceHintsController {
+ public:
+  ResourceHintsController();
+  ~ResourceHintsController();
+  int PreresolveUrl(net::URLRequestContextGetter* getter,
+                    const GURL& url,
+                    const net::CompletionCallback& callback);
+
+ private:
+  struct DnsRequest {
+    DnsRequest(net::HostResolver* resolver);
+    net::SingleRequestHostResolver resolver;
+    net::AddressList addresses;
+  };
+
+  void OnResolveComplete(DnsRequest* request,
+                         const net::CompletionCallback& callback,
+                         int result);
+
+  std::set<DnsRequest*> pending_dns_requests_;
+
+  DISALLOW_COPY_AND_ASSIGN(ResourceHintsController);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_LOADER_RESOURCE_HINTS_IMPL_H_