Fix HTMLPreloadScanner handling of type in link preload.

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 164 matching lines @@
             String("Preconnect CORS setting is ") +
                 String((crossOrigin == CrossOriginAttributeAnonymous)
                            ? "anonymous"
                            : "use-credentials")));
       }
     }
     networkHintsInterface.preconnectHost(href, crossOrigin);
   }
 }
 
-bool LinkLoader::getResourceTypeFromAsAttribute(const String& as,
-                                                Resource::Type& type) {
+WTF::Optional<Resource::Type> LinkLoader::getResourceTypeFromAsAttribute(
+    const String& as) {
   DCHECK_EQ(as.lower(), as);
   if (as == "image") {
-    type = Resource::Image;
+    return Resource::Image;
   } else if (as == "script") {
-    type = Resource::Script;
+    return Resource::Script;
   } else if (as == "style") {
-    type = Resource::CSSStyleSheet;
+    return Resource::CSSStyleSheet;
   } else if (as == "media") {
-    type = Resource::Media;
+    return Resource::Media;
   } else if (as == "font") {
-    type = Resource::Font;
+    return Resource::Font;
   } else if (as == "track") {
-    type = Resource::TextTrack;
+    return Resource::TextTrack;
   } else {
-    type = Resource::Raw;
     if (!as.isEmpty())

[Charlie Harrison, 2017/01/10 14:35:06]

Can this condition be an "else if" in the outer else if chain?

[Yoav Weiss, 2017/01/11 05:14:36]

Yeah (more or less). done

-      return false;
+      return WTF::nullopt;
+    return Resource::Raw;
   }
-  return true;
 }
 
 void LinkLoader::createLinkPreloadResourceClient(Resource* resource) {
   if (!resource)
     return;
   switch (resource->getType()) {
     case Resource::Image:
       m_linkPreloadResourceClient = LinkPreloadImageResourceClient::create(
           this, toImageResource(resource));
       break;
@@ skipping 77 matching lines @@
     }
 
     // Preload only if media matches
     MediaQuerySet* mediaQueries = MediaQuerySet::create(media);
     MediaQueryEvaluator evaluator(*mediaValues);
     if (!evaluator.eval(mediaQueries))
       return nullptr;
   }
   if (caller == LinkCalledFromHeader)
     UseCounter::count(document, UseCounter::LinkHeaderPreload);
-  Resource::Type resourceType;
-  if (!LinkLoader::getResourceTypeFromAsAttribute(as, resourceType)) {
+  Optional<Resource::Type> resourceType =
+      LinkLoader::getResourceTypeFromAsAttribute(as);
+  if (resourceType == WTF::nullopt) {
     document.addConsoleMessage(ConsoleMessage::create(
         OtherMessageSource, WarningMessageLevel,
         String("<link rel=preload> must have a valid `as` value")));
     errorOccurred = true;
     return nullptr;
   }
 
-  if (!isSupportedType(resourceType, mimeType)) {
+  if (!isSupportedType(resourceType.value(), mimeType)) {
     document.addConsoleMessage(ConsoleMessage::create(
         OtherMessageSource, WarningMessageLevel,
         String("<link rel=preload> has an unsupported `type` value")));
     return nullptr;
   }
   ResourceRequest resourceRequest(document.completeURL(href));
-  ResourceFetcher::determineRequestContext(resourceRequest, resourceType,
-                                           false);
+  ResourceFetcher::determineRequestContext(resourceRequest,
+                                           resourceType.value(), false);
 
   if (referrerPolicy != ReferrerPolicyDefault) {
     resourceRequest.setHTTPReferrer(SecurityPolicy::generateReferrer(
         referrerPolicy, href, document.outgoingReferrer()));
   }
 
   FetchRequest linkRequest(resourceRequest, FetchInitiatorTypeNames::link,
                            document.encodingName());
 
   if (crossOrigin != CrossOriginAttributeNotSet) {
     linkRequest.setCrossOriginAccessControl(document.getSecurityOrigin(),
                                             crossOrigin);
   }
   Settings* settings = document.settings();
   if (settings && settings->getLogPreload()) {
     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);
+  return document.loader()->startPreload(resourceType.value(), linkRequest);
 }
 
 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);
 
@@ skipping 134 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