Make generateReferrerHeader() return a Referrer instead of a String

Source/platform/network/ResourceRequest.h

Index: Source/platform/network/ResourceRequest.h
diff --git a/Source/platform/network/ResourceRequest.h b/Source/platform/network/ResourceRequest.h
index faf9fc5660e4635c4757a806794aff556525ca50..67be8211f019cd143cb95c43ca6263882e8cebc9 100644
--- a/Source/platform/network/ResourceRequest.h
+++ b/Source/platform/network/ResourceRequest.h
@@ -113,7 +113,7 @@ public:
 
     const AtomicString& httpReferrer() const { return httpHeaderField("Referer"); }
     ReferrerPolicy referrerPolicy() const { return m_referrerPolicy; }
-    void setHTTPReferrer(const Referrer& httpReferrer) { setHTTPHeaderField("Referer", httpReferrer.referrer); m_referrerPolicy = httpReferrer.referrerPolicy; }
+    void setHTTPReferrer(const Referrer&);
     void clearHTTPReferrer();
 
     const AtomicString& httpOrigin() const { return httpHeaderField("Origin"); }