Declarative resource hints go through mojo IPC to //content

third_party/WebKit/Source/core/loader/NetworkHintsInterface.h

 // Copyright 2015 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 NetworkHintsInterface_h
 #define NetworkHintsInterface_h
 
 #include "platform/network/NetworkHints.h"
 
 namespace blink {
 
 class NetworkHintsInterface {
 public:
-    virtual void dnsPrefetchHost(const String&) const = 0;
+    virtual void dnsPrefetchHost(const KURL&) const = 0;
     virtual void preconnectHost(const KURL&, const CrossOriginAttributeValue) const = 0;
 };
 
 class NetworkHintsInterfaceImpl : public NetworkHintsInterface {
-    void dnsPrefetchHost(const String& host) const override
+    void dnsPrefetchHost(const KURL& url) const override
     {
-        prefetchDNS(host);
+        prefetchDNS(url);
     }
 
     void preconnectHost(const KURL& host, const CrossOriginAttributeValue crossOrigin) const override
     {
         preconnect(host, crossOrigin);
     }
 };
 
 } // namespace blink
 
 #endif