Fix HTMLPreloadScanner handling of type in link preload.

third_party/WebKit/Source/core/loader/LinkLoader.h

 /*
  * 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 23 matching lines @@
 
 #include "core/CoreExport.h"
 #include "core/fetch/ResourceClient.h"
 #include "core/fetch/ResourceOwner.h"
 #include "core/loader/LinkLoaderClient.h"
 #include "core/loader/resource/LinkPreloadResourceClients.h"
 #include "platform/CrossOriginAttributeValue.h"
 #include "platform/PrerenderClient.h"
 #include "platform/Timer.h"
 #include "platform/heap/Handle.h"
+#include "wtf/Optional.h"
 
 namespace blink {
 
 class Document;
 class LinkRelAttribute;
 class NetworkHintsInterface;
 class PrerenderHandle;
 struct ViewportDescriptionWrapper;
 
 // The LinkLoader can load link rel types icon, dns-prefetch, subresource,
@@ skipping 40 matching lines @@
   // Media links cannot be preloaded until the first chunk is parsed. The rest
   // can be preloaded at commit time.
   enum MediaPreloadPolicy { LoadAll, OnlyLoadNonMedia, OnlyLoadMedia };
   static void loadLinksFromHeader(const String& headerValue,
                                   const KURL& baseURL,
                                   Document*,
                                   const NetworkHintsInterface&,
                                   CanLoadResources,
                                   MediaPreloadPolicy,
                                   ViewportDescriptionWrapper*);
-  static bool getResourceTypeFromAsAttribute(const String& as, Resource::Type&);
+  static WTF::Optional<Resource::Type> getResourceTypeFromAsAttribute(
+      const String& as);
 
   DECLARE_TRACE();
 
  private:
   explicit LinkLoader(LinkLoaderClient*);
 
   void linkLoadTimerFired(TimerBase*);
   void linkLoadingErrorTimerFired(TimerBase*);
   void createLinkPreloadResourceClient(Resource*);
 
   Member<LinkLoaderClient> m_client;
 
   Timer<LinkLoader> m_linkLoadTimer;
   Timer<LinkLoader> m_linkLoadingErrorTimer;
 
   Member<PrerenderHandle> m_prerender;
   Member<LinkPreloadResourceClient> m_linkPreloadResourceClient;
 };
 
 }  // namespace blink
 
 #endif