Make ClientHintsPreferences class work like a class.

Source/core/html/parser/PreloadRequest.cpp

 // 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.
 
 #include "config.h"
 #include "core/html/parser/PreloadRequest.h"
 
 #include "core/dom/Document.h"
 #include "core/fetch/FetchInitiatorInfo.h"
 
@@ skipping 28 matching lines @@
         request.setCrossOriginAccessControl(securityOrigin,
             sameOrigin ? AllowStoredCredentials : DoNotAllowStoredCredentials,
             ClientDidNotRequestCredentials);
     }
 
     if (m_isCORSEnabled)
         request.setCrossOriginAccessControl(document->securityOrigin(), m_allowCredentials);
 
     request.setDefer(m_defer);
     request.setResourceWidth(m_resourceWidth);
-    request.setClientHintsPreferences(m_clientHintsPreferences);
+    request.clientHintsPreferences().updateFrom(m_clientHintsPreferences);
 
     return request;
 }
 
 }