Implement referrerpolicy attribute for img elements

Source/core/html/parser/HTMLPreloadScanner.cpp

Index: Source/core/html/parser/HTMLPreloadScanner.cpp
diff --git a/Source/core/html/parser/HTMLPreloadScanner.cpp b/Source/core/html/parser/HTMLPreloadScanner.cpp
index 055e811b23f9025c037f00a0e4963680a3e4e484..b64bec1b625396823c94c3afa94a7013c521f586 100644
--- a/Source/core/html/parser/HTMLPreloadScanner.cpp
+++ b/Source/core/html/parser/HTMLPreloadScanner.cpp
@@ -593,7 +593,18 @@ void TokenPreloadScanner::scanCommon(const Token& token, const SegmentedString&
         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;