Implement referrerpolicy attribute for img elements

Source/core/html/parser/HTMLPreloadScanner.cpp

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * Copyright (C) 2009 Torch Mobile, Inc. http://www.torchmobile.com/
  * Copyright (C) 2010 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 575 matching lines @@
         if (match(tagImpl, pictureTag)) {
             m_inPicture = true;
             m_pictureData = PictureData();
             return;
         }
 
         StartTagScanner scanner(tagImpl, m_documentParameters->mediaValues);
         scanner.processAttributes(token.attributes());
         if (m_inPicture)
             scanner.handlePictureSourceURL(m_pictureData);
-        OwnPtr<PreloadRequest> request = scanner.createPreloadRequest(m_predictedBaseElementURL, source, m_clientHintsPreferences, m_pictureData, m_documentParameters->referrerPolicy);
+
+        ReferrerPolicy referrerPolicy = m_documentParameters->referrerPolicy;
+        const typename Token::Attribute* referrerPolicyAttribute = token.getAttributeItem(referrerpolicyAttr);
+        if (referrerPolicyAttribute) {
+            String referrerPolicyValue(referrerPolicyAttribute->value);
+            ReferrerPolicy parsedReferrerPolicy;
+            if (SecurityPolicy::referrerPolicyFromString(referrerPolicyValue, &parsedReferrerPolicy)) {
+                referrerPolicy = parsedReferrerPolicy;
+            }
+        }

[Yoav Weiss, 2015/08/18 07:22:17]

I don't think we should handle the referrer attribute here. It should probably
be handled as part of processImgAttribute for this change, since we want to
enable it only on img elements, right?

[estark, 2015/08/18 17:34:26]

Hmm, I originally put it here because the spec defines it for multiple elements,
not just img (e.g. <iframe> and <a>), but after looking more closely, it seems
the <img> is the only relevant element for which we send a preload request, so I
think you're right. Done. (Though that does require adding a m_referrerPolicy
member to StartTagScanner, IIUC.)

+
+        OwnPtr<PreloadRequest> request = scanner.createPreloadRequest(m_predictedBaseElementURL, source, m_clientHintsPreferences, m_pictureData, referrerPolicy);
         if (request)
             requests.append(request.release());
         return;
     }
     default: {
         return;
     }
     }
 }
 
@@ skipping 54 matching lines @@
     else
         mediaValues = MediaValuesCached::create(*document);
     ASSERT(mediaValues->isSafeToSendToAnotherThread());
     defaultViewportMinWidth = document->viewportDefaultMinWidth();
     viewportMetaZeroValuesQuirk = document->settings() && document->settings()->viewportMetaZeroValuesQuirk();
     viewportMetaEnabled = document->settings() && document->settings()->viewportMetaEnabled();
     referrerPolicy = ReferrerPolicyDefault;
 }
 
 }