Adding Link header support for dns-prefetch

Source/core/loader/LinkLoader.cpp

 /*
  * Copyright (C) 2011 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 95 matching lines @@
 void LinkLoader::didSendLoadForPrerender()
 {
     m_client->didSendLoadForLinkPrerender();
 }
 
 void LinkLoader::didSendDOMContentLoadedForPrerender()
 {
     m_client->didSendDOMContentLoadedForLinkPrerender();
 }
 
-bool LinkLoader::loadLink(const LinkRelAttribute& relAttribute, const AtomicString& crossOriginMode, const String& type, const KURL& href, Document& document)
+static void dnsPrefetchIfNeeded(const LinkRelAttribute& relAttribute, const KURL& href, Document& document)
 {
     if (relAttribute.isDNSPrefetch()) {
         Settings* settings = document.settings();
         // FIXME: The href attribute of the link element can be in "//hostname" form, and we shouldn't attempt
         // to complete that as URL <https://bugs.webkit.org/show_bug.cgi?id=48857>.
         if (settings && settings->dnsPrefetchingEnabled() && href.isValid() && !href.isEmpty()) {
             if (settings->logDnsPrefetchAndPreconnect())
                 document.addConsoleMessage(ConsoleMessage::create(OtherMessageSource, DebugMessageLevel, String("DNS prefetch triggered for " + href.host())));
             prefetchDNS(href.host());
         }
     }
+}
+
+bool LinkLoader::loadLinkFromHeader(const String& headerValue, Document* document)
+{
+    if (!document)
+        return false;
+    LinkHeaderSet headerSet(headerValue);
+    for (auto& header : headerSet) {
+        if (!header.valid() || header.url().isEmpty() || header.rel().isEmpty())
+            return false;
+        LinkRelAttribute relAttribute(header.rel());
+        KURL url = document->completeURL(header.url());
+        dnsPrefetchIfNeeded(relAttribute, url, *document);
+
+        // FIXME: Add more supported headers as needed.
+    }
+    return true;
+}
+
+bool LinkLoader::loadLink(const LinkRelAttribute& relAttribute, const AtomicString& crossOriginMode, const String& type, const KURL& href, Document& document)
+{
+    dnsPrefetchIfNeeded(relAttribute, href, document);
 
     if (relAttribute.isPreconnect() && href.isValid()) {
         preconnect(href);
     }
 
     // FIXME(crbug.com/323096): Should take care of import.
     if ((relAttribute.isLinkPrefetch() || relAttribute.isLinkSubresource() || relAttribute.isTransitionExitingStylesheet()) && href.isValid() && document.frame()) {
         if (!m_client->shouldLoadLink())
             return false;
         Resource::Type type = relAttribute.isLinkSubresource() ?  Resource::LinkSubresource : Resource::LinkPrefetch;
@@ skipping 27 matching lines @@
         m_prerender.clear();
     }
 }
 
 void LinkLoader::trace(Visitor* visitor)
 {
     visitor->trace(m_prerender);
 }
 
 }