Prefetch Link header support.

third_party/WebKit/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 324 matching lines @@
   if (settings && settings->logPreload()) {
     document.addConsoleMessage(ConsoleMessage::create(
         OtherMessageSource, DebugMessageLevel,
         String("Preload triggered for " + href.host() + href.path())));
   }
   linkRequest.setForPreload(true, monotonicallyIncreasingTime());
   linkRequest.setLinkPreload(true);
   return document.loader()->startPreload(resourceType, linkRequest);
 }
 
-void LinkLoader::prefetchIfNeeded(Document& document,
+static Resource* prefetchIfNeeded(Document& document,
                                   const KURL& href,
                                   const LinkRelAttribute& relAttribute,
                                   CrossOriginAttributeValue crossOrigin,
                                   ReferrerPolicy referrerPolicy) {
   if (relAttribute.isLinkPrefetch() && href.isValid() && document.frame()) {
     UseCounter::count(document, UseCounter::LinkRelPrefetch);
 
     FetchRequest linkRequest(ResourceRequest(document.completeURL(href)),
                              FetchInitiatorTypeNames::link);
     if (referrerPolicy != ReferrerPolicyDefault) {
       linkRequest.mutableResourceRequest().setHTTPReferrer(
           SecurityPolicy::generateReferrer(referrerPolicy, href,
                                            document.outgoingReferrer()));
     }
     if (crossOrigin != CrossOriginAttributeNotSet) {
       linkRequest.setCrossOriginAccessControl(document.getSecurityOrigin(),
                                               crossOrigin);
     }
-    setResource(LinkFetchResource::fetch(Resource::LinkPrefetch, linkRequest,
-                                         document.fetcher()));
+    return LinkFetchResource::fetch(Resource::LinkPrefetch, linkRequest,
+                                    document.fetcher());
   }
+  return nullptr;
 }
 
 void LinkLoader::loadLinksFromHeader(
     const String& headerValue,
     const KURL& baseURL,
     Document* document,
     const NetworkHintsInterface& networkHintsInterface,
     CanLoadResources canLoadResources,
     MediaPreloadPolicy mediaPolicy,
     ViewportDescriptionWrapper* viewportDescriptionWrapper) {
@@ skipping 22 matching lines @@
                          crossOriginAttributeValue(header.crossOrigin()),
                          networkHintsInterface, LinkCalledFromHeader);
     }
     if (canLoadResources != DoNotLoadResources) {
       bool errorOccurred = false;
       ViewportDescription* viewportDescription =
           (viewportDescriptionWrapper && viewportDescriptionWrapper->set)
               ? &(viewportDescriptionWrapper->description)
               : nullptr;
 
+      CrossOriginAttributeValue crossOrigin =
+          crossOriginAttributeValue(header.crossOrigin());
       preloadIfNeeded(relAttribute, url, *document, header.as(),
-                      header.mimeType(), header.media(),
-                      crossOriginAttributeValue(header.crossOrigin()),
+                      header.mimeType(), header.media(), crossOrigin,
                       LinkCalledFromHeader, errorOccurred, viewportDescription,
                       ReferrerPolicyDefault);
+      prefetchIfNeeded(*document, url, relAttribute, crossOrigin,
+                       ReferrerPolicyDefault);
     }
     if (relAttribute.isServiceWorker()) {
       UseCounter::count(*document, UseCounter::LinkHeaderServiceWorker);
     }
     // TODO(yoav): Add more supported headers as needed.
   }
 }
 
 bool LinkLoader::loadLink(const LinkRelAttribute& relAttribute,
                           CrossOriginAttributeValue crossOrigin,
@@ skipping 16 matching lines @@
   bool errorOccurred = false;
   createLinkPreloadResourceClient(preloadIfNeeded(
       relAttribute, href, document, as, type, media, crossOrigin,
       LinkCalledFromMarkup, errorOccurred, nullptr, referrerPolicy));
   if (errorOccurred)
     m_linkLoadingErrorTimer.startOneShot(0, BLINK_FROM_HERE);
 
   if (href.isEmpty() || !href.isValid())
     released();
 
-  prefetchIfNeeded(document, href, relAttribute, crossOrigin, referrerPolicy);
+  Resource* resource = prefetchIfNeeded(document, href, relAttribute,
+                                        crossOrigin, referrerPolicy);
+  if (resource)
+    setResource(resource);
 
   if (const unsigned prerenderRelTypes =
           prerenderRelTypesFromRelAttribute(relAttribute, document)) {
     if (!m_prerender) {
       m_prerender =
           PrerenderHandle::create(document, this, href, prerenderRelTypes);
     } else if (m_prerender->url() != href) {
       m_prerender->cancel();
       m_prerender =
           PrerenderHandle::create(document, this, href, prerenderRelTypes);
@@ skipping 19 matching lines @@
 
 DEFINE_TRACE(LinkLoader) {
   visitor->trace(m_client);
   visitor->trace(m_prerender);
   visitor->trace(m_linkPreloadResourceClient);
   ResourceOwner<Resource, ResourceClient>::trace(visitor);
   PrerenderClient::trace(visitor);
 }
 
 }  // namespace blink