Source/WebCore/loader/LinkLoader.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2016 Apple 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
  * copyright notice, this list of conditions and the following disclaimer
  * in the documentation and/or other materials provided with the
  * distribution.
  *     * Neither the name of Google Inc. nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */

 #include "config.h"
 #include "LinkLoader.h"

 #include "CSSStyleSheet.h"
 #include "CachedCSSStyleSheet.h"
 #include "CachedResourceLoader.h"
 #include "CachedResourceRequest.h"
 #include "ContainerNode.h"
 #include "CrossOriginAccessControl.h"
 #include "Document.h"
 #include "Frame.h"
 #include "FrameLoader.h"
 #include "FrameLoaderClient.h"
 #include "FrameView.h"
 #include "LinkHeader.h"
 #include "LinkPreloadResourceClients.h"
 #include "LinkRelAttribute.h"
 #include "MIMETypeRegistry.h"
 #include "MediaQueryEvaluator.h"
 #include "RuntimeEnabledFeatures.h"
 #include "Settings.h"
 #include "StyleResolver.h"

 namespace WebCore {

 LinkLoader::LinkLoader(LinkLoaderClient& client)
     : m_client(client)
     , m_weakPtrFactory(this)
 {
 }

 LinkLoader::~LinkLoader()
 {
     if (m_cachedLinkResource)
         m_cachedLinkResource->removeClient(*this);
     if (m_preloadResourceClient)
         m_preloadResourceClient->clear();
 }

 void LinkLoader::triggerEvents(const CachedResource& resource)
 {
     if (resource.errorOccurred())
         m_client.linkLoadingErrored();
     else
         m_client.linkLoaded();
 }

 void LinkLoader::notifyFinished(CachedResource& resource)
 {
     ASSERT_UNUSED(resource, m_cachedLinkResource.get() == &resource);

     triggerEvents(*m_cachedLinkResource);

     m_cachedLinkResource->removeClient(*this);
     m_cachedLinkResource = nullptr;
 }

 void LinkLoader::loadLinksFromHeader(const String& headerValue, const URL& baseURL, Document& document, MediaAttributeCheck mediaAttributeCheck)
 {
     if (headerValue.isEmpty())
         return;
     LinkHeaderSet headerSet(headerValue);
     for (auto& header : headerSet) {
         if (!header.valid() || header.url().isEmpty() || header.rel().isEmpty())
             continue;
         if (mediaAttributeCheck == MediaAttributeCheck::MediaAttributeNotEmpty) {
             if (header.media().isEmpty())
                 continue;
         } else {
             if (!header.media().isEmpty())
                 continue;
         }

         LinkRelAttribute relAttribute(header.rel());
         URL url(baseURL, header.url());
         // Sanity check to avoid re-entrancy here.
         if (equalIgnoringFragmentIdentifier(url, baseURL))
             continue;
         preloadIfNeeded(relAttribute, url, document, header.as(), header.media(), header.mimeType(), header.crossOrigin(), nullptr);
     }
 }

 std::optional<CachedResource::Type> LinkLoader::resourceTypeFromAsAttribute(const String& as)
 {
     if (equalLettersIgnoringASCIICase(as, "fetch"))
         return CachedResource::RawResource;
     if (equalLettersIgnoringASCIICase(as, "image"))
         return CachedResource::ImageResource;
     if (equalLettersIgnoringASCIICase(as, "script"))
         return CachedResource::Script;
     if (equalLettersIgnoringASCIICase(as, "style"))
         return CachedResource::CSSStyleSheet;
     if (RuntimeEnabledFeatures::sharedFeatures().mediaPreloadingEnabled() && (equalLettersIgnoringASCIICase(as, "video") || equalLettersIgnoringASCIICase(as, "audio")))
         return CachedResource::MediaResource;
     if (equalLettersIgnoringASCIICase(as, "font"))
         return CachedResource::FontResource;
 #if ENABLE(VIDEO_TRACK)
     if (equalLettersIgnoringASCIICase(as, "track"))
         return CachedResource::TextTrackResource;
 #endif
     return std::nullopt;
 }

 static std::unique_ptr<LinkPreloadResourceClient> createLinkPreloadResourceClient(CachedResource& resource, LinkLoader& loader, CachedResource::Type type)
 {
     switch (type) {
     case CachedResource::ImageResource:
         return LinkPreloadImageResourceClient::create(loader, static_cast<CachedImage&>(resource));
     case CachedResource::Script:
         return LinkPreloadScriptResourceClient::create(loader, static_cast<CachedScript&>(resource));
     case CachedResource::CSSStyleSheet:
         return LinkPreloadStyleResourceClient::create(loader, static_cast<CachedCSSStyleSheet&>(resource));
     case CachedResource::FontResource:
         return LinkPreloadFontResourceClient::create(loader, static_cast<CachedFont&>(resource));
     case CachedResource::MediaResource:
         if (!RuntimeEnabledFeatures::sharedFeatures().mediaPreloadingEnabled())
             ASSERT_NOT_REACHED();
         FALLTHROUGH;
 #if ENABLE(VIDEO_TRACK)
     case CachedResource::TextTrackResource:
 #endif
     case CachedResource::RawResource:
         return LinkPreloadRawResourceClient::create(loader, static_cast<CachedRawResource&>(resource));
     case CachedResource::MainResource:
     case CachedResource::Icon:
 #if ENABLE(SVG_FONTS)
     case CachedResource::SVGFontResource:
 #endif
     case CachedResource::SVGDocumentResource:
 #if ENABLE(XSLT)
     case CachedResource::XSLStyleSheet:
 #endif
 #if ENABLE(LINK_PREFETCH)
     case CachedResource::LinkSubresource:
     case CachedResource::LinkPrefetch:
 #endif
         // None of these values is currently supported as an `as` value.
         ASSERT_NOT_REACHED();
     }
     return nullptr;
 }

 bool LinkLoader::isSupportedType(CachedResource::Type resourceType, const String& mimeType)
 {
     if (mimeType.isEmpty())
         return true;
     switch (resourceType) {
     case CachedResource::ImageResource:
         return MIMETypeRegistry::isSupportedImageOrSVGMIMEType(mimeType);
     case CachedResource::Script:
         return MIMETypeRegistry::isSupportedJavaScriptMIMEType(mimeType);
     case CachedResource::CSSStyleSheet:
         return MIMETypeRegistry::isSupportedStyleSheetMIMEType(mimeType);
     case CachedResource::FontResource:
         return MIMETypeRegistry::isSupportedFontMIMEType(mimeType);
     case CachedResource::MediaResource:
         if (!RuntimeEnabledFeatures::sharedFeatures().mediaPreloadingEnabled())
             ASSERT_NOT_REACHED();
         return MIMETypeRegistry::isSupportedMediaMIMEType(mimeType);

 #if ENABLE(VIDEO_TRACK)
     case CachedResource::TextTrackResource:
         return MIMETypeRegistry::isSupportedTextTrackMIMEType(mimeType);
 #endif
     case CachedResource::RawResource:
         return true;
     default:
         ASSERT_NOT_REACHED();
     }
     return false;
 }

 std::unique_ptr<LinkPreloadResourceClient> LinkLoader::preloadIfNeeded(const LinkRelAttribute& relAttribute, const URL& href, Document& document, const String& as, const String& media, const String& mimeType, const String& crossOriginMode, LinkLoader* loader)
 {
     if (!document.loader() || !relAttribute.isLinkPreload)
         return nullptr;

     ASSERT(RuntimeEnabledFeatures::sharedFeatures().linkPreloadEnabled());
     if (!href.isValid()) {
         document.addConsoleMessage(MessageSource::Other, MessageLevel::Error, String("<link rel=preload> has an invalid `href` value"));
         return nullptr;
     }
     auto type = LinkLoader::resourceTypeFromAsAttribute(as);
     if (!type) {
         document.addConsoleMessage(MessageSource::Other, MessageLevel::Error, String("<link rel=preload> must have a valid `as` value"));
         return nullptr;
     }
     if (!MediaQueryEvaluator::mediaAttributeMatches(document, media))
         return nullptr;
     if (!isSupportedType(type.value(), mimeType))
         return nullptr;

     ResourceRequest resourceRequest(document.completeURL(href));
     resourceRequest.setIgnoreForRequestCount(true);
     CachedResourceRequest linkRequest(WTFMove(resourceRequest), CachedResourceLoader::defaultCachedResourceOptions(), CachedResource::defaultPriorityForResourceType(type.value()));
     linkRequest.setInitiator("link");
     linkRequest.setIsLinkPreload();

     linkRequest.setAsPotentiallyCrossOrigin(crossOriginMode, document);
     CachedResourceHandle<CachedResource> cachedLinkResource = document.cachedResourceLoader().preload(type.value(), WTFMove(linkRequest));

     if (cachedLinkResource && loader)
         return createLinkPreloadResourceClient(*cachedLinkResource, *loader, type.value());
     return nullptr;
 }

 void LinkLoader::cancelLoad()
 {
     if (m_preloadResourceClient)
         m_preloadResourceClient->clear();
 }

 bool LinkLoader::loadLink(const LinkRelAttribute& relAttribute, const URL& href, const String& as, const String& media, const String& mimeType, const String& crossOrigin, Document& document)
 {
     if (relAttribute.isDNSPrefetch) {
         // 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 (document.settings().dnsPrefetchingEnabled() && href.isValid() && !href.isEmpty() && document.frame())
             document.frame()->loader().client().prefetchDNS(href.host());
     }

     if (m_client.shouldLoadLink()) {
         auto resourceClient = preloadIfNeeded(relAttribute, href, document, as, media, mimeType, crossOrigin, this);
         if (resourceClient)
             m_preloadResourceClient = WTFMove(resourceClient);
         else if (m_preloadResourceClient)
             m_preloadResourceClient->clear();
     }

 #if ENABLE(LINK_PREFETCH)
     if ((relAttribute.isLinkPrefetch || relAttribute.isLinkSubresource) && href.isValid() && document.frame()) {
         if (!m_client.shouldLoadLink())
             return false;

         std::optional<ResourceLoadPriority> priority;
         CachedResource::Type type = CachedResource::LinkPrefetch;
         if (relAttribute.isLinkSubresource) {
             // We only make one request to the cached resource loader if multiple rel types are specified;
             // this is the higher priority, which should overwrite the lower priority.
             priority = ResourceLoadPriority::Low;
             type = CachedResource::LinkSubresource;
         }

         if (m_cachedLinkResource) {
             m_cachedLinkResource->removeClient(*this);
             m_cachedLinkResource = nullptr;
         }
         ResourceLoaderOptions options = CachedResourceLoader::defaultCachedResourceOptions();
         options.contentSecurityPolicyImposition = ContentSecurityPolicyImposition::SkipPolicyCheck;
         m_cachedLinkResource = document.cachedResourceLoader().requestLinkResource(type, CachedResourceRequest(ResourceRequest(document.completeURL(href)), options, priority));
         if (m_cachedLinkResource)
             m_cachedLinkResource->addClient(*this);
     }
 #endif

     return true;
 }

 }
	/*
	* Copyright (C) 2011 Google Inc. All rights reserved.
	* Copyright (C) 2016 Apple 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
	* copyright notice, this list of conditions and the following disclaimer
	* in the documentation and/or other materials provided with the
	* distribution.
	* * Neither the name of Google Inc. nor the names of its
	* contributors may be used to endorse or promote products derived from
	* this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
	* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
	* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
	* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
	* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
	* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
	* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*
	*/

	#include "config.h"
	#include "LinkLoader.h"

	#include "CSSStyleSheet.h"
	#include "CachedCSSStyleSheet.h"
	#include "CachedResourceLoader.h"
	#include "CachedResourceRequest.h"
	#include "ContainerNode.h"
	#include "CrossOriginAccessControl.h"
	#include "Document.h"
	#include "Frame.h"
	#include "FrameLoader.h"
	#include "FrameLoaderClient.h"
	#include "FrameView.h"
	#include "LinkHeader.h"
	#include "LinkPreloadResourceClients.h"
	#include "LinkRelAttribute.h"
	#include "MIMETypeRegistry.h"
	#include "MediaQueryEvaluator.h"
	#include "RuntimeEnabledFeatures.h"
	#include "Settings.h"
	#include "StyleResolver.h"

	namespace WebCore {

	LinkLoader::LinkLoader(LinkLoaderClient& client)
	: m_client(client)
	, m_weakPtrFactory(this)
	{
	}

	LinkLoader::~LinkLoader()
	{
	if (m_cachedLinkResource)
	m_cachedLinkResource->removeClient(*this);
	if (m_preloadResourceClient)
	m_preloadResourceClient->clear();
	}

	void LinkLoader::triggerEvents(const CachedResource& resource)
	{
	if (resource.errorOccurred())
	m_client.linkLoadingErrored();
	else
	m_client.linkLoaded();
	}

	void LinkLoader::notifyFinished(CachedResource& resource)
	{
	ASSERT_UNUSED(resource, m_cachedLinkResource.get() == &resource);

	triggerEvents(*m_cachedLinkResource);

	m_cachedLinkResource->removeClient(*this);
	m_cachedLinkResource = nullptr;
	}

	void LinkLoader::loadLinksFromHeader(const String& headerValue, const URL& baseURL, Document& document, MediaAttributeCheck mediaAttributeCheck)
	{
	if (headerValue.isEmpty())
	return;
	LinkHeaderSet headerSet(headerValue);
	for (auto& header : headerSet) {
	if (!header.valid() \|\| header.url().isEmpty() \|\| header.rel().isEmpty())
	continue;
	if (mediaAttributeCheck == MediaAttributeCheck::MediaAttributeNotEmpty) {
	if (header.media().isEmpty())
	continue;
	} else {
	if (!header.media().isEmpty())
	continue;
	}

	LinkRelAttribute relAttribute(header.rel());
	URL url(baseURL, header.url());
	// Sanity check to avoid re-entrancy here.
	if (equalIgnoringFragmentIdentifier(url, baseURL))
	continue;
	preloadIfNeeded(relAttribute, url, document, header.as(), header.media(), header.mimeType(), header.crossOrigin(), nullptr);
	}
	}

	std::optional<CachedResource::Type> LinkLoader::resourceTypeFromAsAttribute(const String& as)
	{
	if (equalLettersIgnoringASCIICase(as, "fetch"))
	return CachedResource::RawResource;
	if (equalLettersIgnoringASCIICase(as, "image"))
	return CachedResource::ImageResource;
	if (equalLettersIgnoringASCIICase(as, "script"))
	return CachedResource::Script;
	if (equalLettersIgnoringASCIICase(as, "style"))
	return CachedResource::CSSStyleSheet;
	if (RuntimeEnabledFeatures::sharedFeatures().mediaPreloadingEnabled() && (equalLettersIgnoringASCIICase(as, "video") \|\| equalLettersIgnoringASCIICase(as, "audio")))
	return CachedResource::MediaResource;
	if (equalLettersIgnoringASCIICase(as, "font"))
	return CachedResource::FontResource;
	#if ENABLE(VIDEO_TRACK)
	if (equalLettersIgnoringASCIICase(as, "track"))
	return CachedResource::TextTrackResource;
	#endif
	return std::nullopt;
	}

	static std::unique_ptr<LinkPreloadResourceClient> createLinkPreloadResourceClient(CachedResource& resource, LinkLoader& loader, CachedResource::Type type)
	{
	switch (type) {
	case CachedResource::ImageResource:
	return LinkPreloadImageResourceClient::create(loader, static_cast<CachedImage&>(resource));
	case CachedResource::Script:
	return LinkPreloadScriptResourceClient::create(loader, static_cast<CachedScript&>(resource));
	case CachedResource::CSSStyleSheet:
	return LinkPreloadStyleResourceClient::create(loader, static_cast<CachedCSSStyleSheet&>(resource));
	case CachedResource::FontResource:
	return LinkPreloadFontResourceClient::create(loader, static_cast<CachedFont&>(resource));
	case CachedResource::MediaResource:
	if (!RuntimeEnabledFeatures::sharedFeatures().mediaPreloadingEnabled())
	ASSERT_NOT_REACHED();
	FALLTHROUGH;
	#if ENABLE(VIDEO_TRACK)
	case CachedResource::TextTrackResource:
	#endif
	case CachedResource::RawResource:
	return LinkPreloadRawResourceClient::create(loader, static_cast<CachedRawResource&>(resource));
	case CachedResource::MainResource:
	case CachedResource::Icon:
	#if ENABLE(SVG_FONTS)
	case CachedResource::SVGFontResource:
	#endif
	case CachedResource::SVGDocumentResource:
	#if ENABLE(XSLT)
	case CachedResource::XSLStyleSheet:
	#endif
	#if ENABLE(LINK_PREFETCH)
	case CachedResource::LinkSubresource:
	case CachedResource::LinkPrefetch:
	#endif
	// None of these values is currently supported as an `as` value.
	ASSERT_NOT_REACHED();
	}
	return nullptr;
	}

	bool LinkLoader::isSupportedType(CachedResource::Type resourceType, const String& mimeType)
	{
	if (mimeType.isEmpty())
	return true;
	switch (resourceType) {
	case CachedResource::ImageResource:
	return MIMETypeRegistry::isSupportedImageOrSVGMIMEType(mimeType);
	case CachedResource::Script:
	return MIMETypeRegistry::isSupportedJavaScriptMIMEType(mimeType);
	case CachedResource::CSSStyleSheet:
	return MIMETypeRegistry::isSupportedStyleSheetMIMEType(mimeType);
	case CachedResource::FontResource:
	return MIMETypeRegistry::isSupportedFontMIMEType(mimeType);
	case CachedResource::MediaResource:
	if (!RuntimeEnabledFeatures::sharedFeatures().mediaPreloadingEnabled())
	ASSERT_NOT_REACHED();
	return MIMETypeRegistry::isSupportedMediaMIMEType(mimeType);

	#if ENABLE(VIDEO_TRACK)
	case CachedResource::TextTrackResource:
	return MIMETypeRegistry::isSupportedTextTrackMIMEType(mimeType);
	#endif
	case CachedResource::RawResource:
	return true;
	default:
	ASSERT_NOT_REACHED();
	}
	return false;
	}

	std::unique_ptr<LinkPreloadResourceClient> LinkLoader::preloadIfNeeded(const LinkRelAttribute& relAttribute, const URL& href, Document& document, const String& as, const String& media, const String& mimeType, const String& crossOriginMode, LinkLoader* loader)
	{
	if (!document.loader() \|\| !relAttribute.isLinkPreload)
	return nullptr;

	ASSERT(RuntimeEnabledFeatures::sharedFeatures().linkPreloadEnabled());
	if (!href.isValid()) {
	document.addConsoleMessage(MessageSource::Other, MessageLevel::Error, String("<link rel=preload> has an invalid `href` value"));
	return nullptr;
	}
	auto type = LinkLoader::resourceTypeFromAsAttribute(as);
	if (!type) {
	document.addConsoleMessage(MessageSource::Other, MessageLevel::Error, String("<link rel=preload> must have a valid `as` value"));
	return nullptr;
	}
	if (!MediaQueryEvaluator::mediaAttributeMatches(document, media))
	return nullptr;
	if (!isSupportedType(type.value(), mimeType))
	return nullptr;

	ResourceRequest resourceRequest(document.completeURL(href));
	resourceRequest.setIgnoreForRequestCount(true);
	CachedResourceRequest linkRequest(WTFMove(resourceRequest), CachedResourceLoader::defaultCachedResourceOptions(), CachedResource::defaultPriorityForResourceType(type.value()));
	linkRequest.setInitiator("link");
	linkRequest.setIsLinkPreload();

	linkRequest.setAsPotentiallyCrossOrigin(crossOriginMode, document);
	CachedResourceHandle<CachedResource> cachedLinkResource = document.cachedResourceLoader().preload(type.value(), WTFMove(linkRequest));

	if (cachedLinkResource && loader)
	return createLinkPreloadResourceClient(cachedLinkResource, loader, type.value());
	return nullptr;
	}

	void LinkLoader::cancelLoad()
	{
	if (m_preloadResourceClient)
	m_preloadResourceClient->clear();
	}

	bool LinkLoader::loadLink(const LinkRelAttribute& relAttribute, const URL& href, const String& as, const String& media, const String& mimeType, const String& crossOrigin, Document& document)
	{
	if (relAttribute.isDNSPrefetch) {
	// 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 (document.settings().dnsPrefetchingEnabled() && href.isValid() && !href.isEmpty() && document.frame())
	document.frame()->loader().client().prefetchDNS(href.host());
	}

	if (m_client.shouldLoadLink()) {
	auto resourceClient = preloadIfNeeded(relAttribute, href, document, as, media, mimeType, crossOrigin, this);
	if (resourceClient)
	m_preloadResourceClient = WTFMove(resourceClient);
	else if (m_preloadResourceClient)
	m_preloadResourceClient->clear();
	}

	#if ENABLE(LINK_PREFETCH)
	if ((relAttribute.isLinkPrefetch \|\| relAttribute.isLinkSubresource) && href.isValid() && document.frame()) {
	if (!m_client.shouldLoadLink())
	return false;

	std::optional<ResourceLoadPriority> priority;
	CachedResource::Type type = CachedResource::LinkPrefetch;
	if (relAttribute.isLinkSubresource) {
	// We only make one request to the cached resource loader if multiple rel types are specified;
	// this is the higher priority, which should overwrite the lower priority.
	priority = ResourceLoadPriority::Low;
	type = CachedResource::LinkSubresource;
	}

	if (m_cachedLinkResource) {
	m_cachedLinkResource->removeClient(*this);
	m_cachedLinkResource = nullptr;
	}
	ResourceLoaderOptions options = CachedResourceLoader::defaultCachedResourceOptions();
	options.contentSecurityPolicyImposition = ContentSecurityPolicyImposition::SkipPolicyCheck;
	m_cachedLinkResource = document.cachedResourceLoader().requestLinkResource(type, CachedResourceRequest(ResourceRequest(document.completeURL(href)), options, priority));
	if (m_cachedLinkResource)
	m_cachedLinkResource->addClient(*this);
	}
	#endif

	return true;
	}

	}