Implement referrerpolicy attribute for anchor elements

Source/core/loader/FrameLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Kris Jordan <krisjordan@gmail.com>
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 686 matching lines @@
     processFragment(url, NavigationWithinSameDocument);
     checkCompleted();
 
     m_frame->localDOMWindow()->statePopped(stateObject ? stateObject : SerializedScriptValue::nullValue());
 }
 
 void FrameLoader::setReferrerForFrameRequest(ResourceRequest& request, ShouldSendReferrer shouldSendReferrer, Document* originDocument)
 {
     if (!originDocument)
         return;
-    // FIXME: This should be an assertion, but there's some plugin code in the chromium repo
-    // that both determines its own referrer and expects to be associated with an originDocument.
-    if (!request.httpReferrer().isEmpty())
+    // Anchor elements with the 'referrerpolicy' attribute will have
+    // already set the referrer on the request.
+    if (request.didSetHTTPReferrer())
         return;
     if (shouldSendReferrer == NeverSendReferrer)
         return;
 
     // Always use the initiating document to generate the referrer.
     // We need to generateReferrer(), because we haven't enforced ReferrerPolicy or https->http
     // referrer suppression yet.
     Referrer referrer = SecurityPolicy::generateReferrer(originDocument->referrerPolicy(), request.url(), originDocument->outgoingReferrer());
 
     request.setHTTPReferrer(referrer);
@@ skipping 768 matching lines @@
     // FIXME: We need a way to propagate insecure requests policy flags to
     // out-of-process frames. For now, we'll always use default behavior.
     if (!parentFrame->isLocalFrame())
         return nullptr;
 
     ASSERT(toLocalFrame(parentFrame)->document());
     return toLocalFrame(parentFrame)->document()->insecureNavigationsToUpgrade();
 }
 
 } // namespace blink