Refactor the forPreload flag to mean speculative preload.

third_party/WebKit/Source/platform/loader/fetch/ResourceFetcher.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All
     rights reserved.
     Copyright (C) 2009 Torch Mobile Inc. http://www.torchmobile.com/
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
@@ skipping 139 matching lines @@
   return ResourceLoadPriorityUnresolved;
 }
 
 }  // namespace
 
 ResourceLoadPriority ResourceFetcher::computeLoadPriority(
     Resource::Type type,
     const ResourceRequest& resourceRequest,
     ResourcePriority::VisibilityStatus visibility,
     FetchRequest::DeferOption deferOption,
-    bool forPreload) {
+    bool speculativePreload) {
   ResourceLoadPriority priority = typeToPriority(type);
 
   // Visible resources (images in practice) get a boost to High priority.
   if (visibility == ResourcePriority::Visible)
     priority = ResourceLoadPriorityHigh;
 
   // Resources before the first image are considered "early" in the document and
   // resources after the first image are "late" in the document.  Important to
   // note that this is based on when the preload scanner discovers a resource
   // for the most part so the main parser may not have reached the image element
   // yet.
   if (type == Resource::Image)
     m_imageFetched = true;
 
   if (FetchRequest::IdleLoad == deferOption) {
     priority = ResourceLoadPriorityVeryLow;
   } else if (type == Resource::Script) {
     // Special handling for scripts.
     // Default/Parser-Blocking/Preload early in document: High (set in
     // typeToPriority)
     // Async/Defer: Low Priority (applies to both preload and parser-inserted)
     // Preload late in document: Medium
-    if (FetchRequest::LazyLoad == deferOption)
+    if (FetchRequest::LazyLoad == deferOption) {
       priority = ResourceLoadPriorityLow;
-    else if (forPreload && m_imageFetched)
+    } else if (speculativePreload && m_imageFetched) {
+      // Speculative preload is used as a signal for scripts at the bottom of
+      // the document.
       priority = ResourceLoadPriorityMedium;
+    }
   } else if (FetchRequest::LazyLoad == deferOption) {
     priority = ResourceLoadPriorityVeryLow;
   }
 
   // A manually set priority acts as a floor. This is used to ensure that
   // synchronous requests are always given the highest possible priority, as
   // well as to ensure that there isn't priority churn if images move in and out
   // of the viewport, or is displayed more than once, both in and out of the
   // viewport.
   return std::max(context().modifyPriorityForExperiments(priority),
@@ skipping 72 matching lines @@
   return resource.get();
 }
 
 bool ResourceFetcher::isControlledByServiceWorker() const {
   return context().isControlledByServiceWorker();
 }
 
 bool ResourceFetcher::resourceNeedsLoad(Resource* resource,
                                         const FetchRequest& request,
                                         RevalidationPolicy policy) {
-  // Defer a font load until it is actually needed unless this is a preload.
-  if (resource->getType() == Resource::Font && !request.forPreload())
+  // Defer a font load until it is actually needed unless this is a link
+  // preload.
+  if (resource->getType() == Resource::Font && !request.isLinkPreload())
     return false;
   if (resource->isImage() && shouldDeferImageLoad(resource->url()))
     return false;
   return policy != Use || resource->stillNeedsLoad();
 }
 
 // Limit the number of URLs in m_validatedURLs to avoid memory bloat.
 // http://crbug.com/52411
 static const int kMaxValidatedURLsSize = 10000;
 
@@ skipping 117 matching lines @@
     const FetchRequest& request,
     const ResourceFactory& factory,
     ResourceRequestBlockedReason blockedReason) {
   Resource* resource = factory.create(request.resourceRequest(),
                                       request.options(), request.charset());
   resource->error(ResourceError::cancelledDueToAccessCheckError(request.url(),
                                                                 blockedReason));
   return resource;
 }
 
-void ResourceFetcher::moveCachedNonBlockingResourceToBlocking(
+void ResourceFetcher::makePreloadedResourceBlockOnloadIfNeeded(
     Resource* resource,
     const FetchRequest& request) {
   // TODO(yoav): Test that non-blocking resources (video/audio/track) continue
   // to not-block even after being preloaded and discovered.
   if (resource && resource->loader() &&
       resource->isLoadEventBlockingResourceType() &&
-      m_nonBlockingLoaders.contains(resource->loader()) &&
-      resource->isLinkPreload() && !request.forPreload()) {
+      resource->isLinkPreload() && !request.isLinkPreload() &&
+      m_nonBlockingLoaders.contains(resource->loader())) {
     m_nonBlockingLoaders.remove(resource->loader());
     m_loaders.insert(resource->loader());
   }
 }
 
 void ResourceFetcher::updateMemoryCacheStats(Resource* resource,
                                              RevalidationPolicy policy,
                                              const FetchRequest& request,
                                              const ResourceFactory& factory,
                                              bool isStaticData) const {
   if (isStaticData)
     return;
 
-  if (request.forPreload()) {
+  if (request.isSpeculativePreload() || request.isLinkPreload()) {
     DEFINE_RESOURCE_HISTOGRAM("Preload.");
   } else {
     DEFINE_RESOURCE_HISTOGRAM("");
   }
 
   // Aims to count Resource only referenced from MemoryCache (i.e. what would be
   // dead if MemoryCache holds weak references to Resource). Currently we check
   // references to Resource from ResourceClient and |m_preloads| only, because
   // they are major sources of references.
   if (resource && !resource->isAlive() &&
@@ skipping 16 matching lines @@
 
   context().populateResourceRequest(
       factory.type(), request.clientHintsPreferences(),
       request.getResourceWidth(), resourceRequest);
 
   if (!request.url().isValid())
     return Abort;
 
   resourceRequest.setPriority(computeLoadPriority(
       factory.type(), request.resourceRequest(), ResourcePriority::NotVisible,
-      request.defer(), request.forPreload()));
+      request.defer(), request.isSpeculativePreload()));
   initializeResourceRequest(resourceRequest, factory.type(), request.defer());
   network_instrumentation::resourcePrioritySet(identifier,
                                                resourceRequest.priority());
 
   blockedReason = context().canRequest(
       factory.type(), resourceRequest,
       MemoryCache::removeFragmentIdentifierIfNeeded(request.url()),
-      request.options(), request.forPreload(), request.getOriginRestriction());
+      request.options(), request.isSpeculativePreload()
+                             ? FetchContext::ReportingPolicy::SuppressReporting
+                             : FetchContext::ReportingPolicy::Report,
+      request.getOriginRestriction());
   if (blockedReason != ResourceRequestBlockedReason::None) {
     DCHECK(!substituteData.forceSynchronousLoad());
     return Block;
   }
 
   context().willStartLoadingResource(
       identifier, resourceRequest, factory.type(),
-      request.options().initiatorInfo.name, request.forPreload());
+      request.options().initiatorInfo.name,
+      (request.isSpeculativePreload()
+           ? FetchContext::V8ActivityLoggingPolicy::SuppressLogging
+           : FetchContext::V8ActivityLoggingPolicy::Log));
   if (!request.url().isValid())
     return Abort;
 
   resourceRequest.setAllowStoredCredentials(
       request.options().allowCredentials == AllowStoredCredentials);
   return Continue;
 }
 
 Resource* ResourceFetcher::requestResource(
     FetchRequest& request,
@@ skipping 28 matching lines @@
     // to be decoded only on demand.  These data URLs are allowed to be
     // processed using the normal ResourceFetcher machinery.
     if (!resource && !isDataUrl && m_archive)
       return nullptr;
   }
   if (!resource) {
     resource =
         memoryCache()->resourceForURL(request.url(), getCacheIdentifier());
   }
 
-  // See if we can use an existing resource from the cache. If so, we need to
-  // move it to be load blocking.
-  moveCachedNonBlockingResourceToBlocking(resource, request);
+  // If we got a preloaded resource from the cache for a non-preload request,
+  // we may need to make it block the onload event.
+  makePreloadedResourceBlockOnloadIfNeeded(resource, request);
 
   const RevalidationPolicy policy = determineRevalidationPolicy(
       factory.type(), request, resource, isStaticData);
   TRACE_EVENT_INSTANT1("blink", "ResourceFetcher::determineRevalidationPolicy",
                        TRACE_EVENT_SCOPE_THREAD, "revalidationPolicy", policy);
 
   updateMemoryCacheStats(resource, policy, request, factory, isStaticData);
 
   switch (policy) {
     case Reload:
       memoryCache()->remove(resource);
     // Fall through
     case Load:
       resource = createResourceForLoading(request, request.charset(), factory);
       break;
     case Revalidate:
       initializeRevalidation(resourceRequest, resource);
       break;
     case Use:
       if (resource->isLinkPreload() && !request.isLinkPreload())
         resource->setLinkPreload(false);
       break;
   }
   if (!resource)
     return nullptr;
   if (resource->getType() != factory.type()) {
-    DCHECK(request.forPreload());
+    DCHECK(request.isSpeculativePreload() || request.isLinkPreload());
+    // TODO(yoav): What's the scenario where this can actually happen?
     return nullptr;
   }
 
   if (!resource->isAlive())
     m_deadStatsRecorder.update(policy);
 
   if (policy != Use)
     resource->setIdentifier(identifier);
 
-  if (!request.forPreload() || policy != Use) {
+  // TODO(yoav): It is not clear why preloads are exempt from this check. Can we
+  // remove the exemption?
+  if (!request.isSpeculativePreload() || policy != Use) {
     // When issuing another request for a resource that is already in-flight
     // make sure to not demote the priority of the in-flight request. If the new
     // request isn't at the same priority as the in-flight request, only allow
     // promotions. This can happen when a visible image's priority is increased
     // and then another reference to the image is parsed (which would be at a
     // lower priority).
     if (resourceRequest.priority() > resource->resourceRequest().priority())
       resource->didChangePriority(resourceRequest.priority(), 0);
+    // TODO(yoav): I'd expect the stated scenario to not go here, as its policy
+    // would be Use.
   }
 
   // If only the fragment identifiers differ, it is the same resource.
   DCHECK(equalIgnoringFragmentIdentifier(resource->url(), request.url()));
   requestLoadStarted(
       identifier, resource, request,
       policy == Use ? ResourceLoadingFromCache : ResourceLoadingFromNetwork,
       isStaticData);
   m_documentResources.set(
       MemoryCache::removeFragmentIdentifierIfNeeded(request.url()), resource);
@@ skipping 101 matching lines @@
   const String cacheIdentifier = getCacheIdentifier();
   DCHECK(!memoryCache()->resourceForURL(request.resourceRequest().url(),
                                         cacheIdentifier));
 
   RESOURCE_LOADING_DVLOG(1) << "Loading Resource for "
                             << request.resourceRequest().url().elidedString();
 
   Resource* resource =
       factory.create(request.resourceRequest(), request.options(), charset);
   resource->setLinkPreload(request.isLinkPreload());
-  if (request.forPreload()) {
+  if (request.isSpeculativePreload()) {
     resource->setPreloadDiscoveryTime(request.preloadDiscoveryTime());
   }
   resource->setCacheIdentifier(cacheIdentifier);
 
   // - Don't add main resource to cache to prevent reuse.
   // - Don't add the resource if its body will not be stored.
   if (factory.type() != Resource::MainResource &&
       request.options().dataBufferingPolicy != DoNotBufferData) {
     memoryCache()->add(resource);
   }
@@ skipping 82 matching lines @@
   if (existingResource->mustRefetchDueToIntegrityMetadata(fetchRequest)) {
     RecordSriResourceIntegrityMismatchEvent(RefetchDueToIntegrityMismatch);
     return Reload;
   }
 
   // Service Worker's CORS fallback message must not be cached.
   if (existingResource->response().wasFallbackRequiredByServiceWorker())
     return Reload;
 
   // We already have a preload going for this URL.
-  if (fetchRequest.forPreload() && existingResource->isPreloaded())
+  if (fetchRequest.isSpeculativePreload() && existingResource->isPreloaded())
     return Use;
 
   // If the same URL has been loaded as a different type, we need to reload.
   if (existingResource->getType() != type) {
     // FIXME: If existingResource is a Preload and the new type is LinkPrefetch
     // We really should discard the new prefetch since the preload has more
     // specific type information! crbug.com/379893
     // fast/dom/HTMLLinkElement/link-and-subresource-test hits this case.
     RESOURCE_LOADING_DVLOG(1) << "ResourceFetcher::determineRevalidationPolicy "
                                  "reloading due to type mismatch.";
@@ skipping 647 matching lines @@
     const KURL& url,
     WebURLRequest::RequestContext requestContext,
     const AtomicString& initiatorName) {
   if (cachedResource(url))
     return;
   ResourceRequest resourceRequest(url);
   resourceRequest.setRequestContext(requestContext);
   FetchRequest request(resourceRequest, initiatorName, resource->options());
   context().canRequest(resource->getType(), resource->lastResourceRequest(),
                        resource->lastResourceRequest().url(), request.options(),
-                       false, request.getOriginRestriction());
+                       FetchContext::ReportingPolicy::Report,
+                       request.getOriginRestriction());
   requestLoadStarted(resource->identifier(), resource, request,
                      ResourceLoadingFromCache);
 }
 
 ResourceFetcher::DeadResourceStatsRecorder::DeadResourceStatsRecorder()
     : m_useCount(0), m_revalidateCount(0), m_loadCount(0) {}
 
 ResourceFetcher::DeadResourceStatsRecorder::~DeadResourceStatsRecorder() {
   DEFINE_THREAD_SAFE_STATIC_LOCAL(
       CustomCountHistogram, hitCountHistogram,
@@ skipping 32 matching lines @@
   visitor->trace(m_context);
   visitor->trace(m_archive);
   visitor->trace(m_loaders);
   visitor->trace(m_nonBlockingLoaders);
   visitor->trace(m_documentResources);
   visitor->trace(m_preloads);
   visitor->trace(m_resourceTimingInfoMap);
 }
 
 }  // namespace blink