Make generateReferrerHeader() return a Referrer instead of a String

Source/platform/exported/WebURLRequest.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 151 matching lines @@
 }
 
 void WebURLRequest::setHTTPHeaderField(const WebString& name, const WebString& value)
 {
     RELEASE_ASSERT(!equalIgnoringCase(name, "referer"));
     m_private->m_resourceRequest->setHTTPHeaderField(name, value);
 }
 
 void WebURLRequest::setHTTPReferrer(const WebString& referrer, WebReferrerPolicy referrerPolicy)
 {
-    if (referrer.isEmpty())
-        m_private->m_resourceRequest->clearHTTPReferrer();
-    else
-        m_private->m_resourceRequest->setHTTPReferrer(Referrer(referrer, static_cast<ReferrerPolicy>(referrerPolicy)));
+    m_private->m_resourceRequest->setHTTPReferrer(Referrer(referrer, static_cast<ReferrerPolicy>(referrerPolicy)));
 }
 
 void WebURLRequest::addHTTPHeaderField(const WebString& name, const WebString& value)
 {
     m_private->m_resourceRequest->addHTTPHeaderField(name, value);
 }
 
 void WebURLRequest::clearHTTPHeaderField(const WebString& name)
 {
     m_private->m_resourceRequest->clearHTTPHeaderField(name);
@@ skipping 192 matching lines @@
     // Subclasses may call this directly so a self-assignment check is needed
     // here as well as in the public assign method.
     if (m_private == p)
         return;
     if (m_private)
         m_private->dispose();
     m_private = p;
 }
 
 } // namespace blink