Make ResourceFetcher return Resources with LoadError instead of nullptrs.

third_party/WebKit/Source/core/fetch/ResourceFetcher.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@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
     License as published by the Free Software Foundation; either
     version 2 of the License, or (at your option) any later version.
@@ skipping 137 matching lines @@
     friend class ResourceCacheValidationSuppressor;
 
     explicit ResourceFetcher(FetchContext*);
 
     void initializeRevalidation(ResourceRequest&, Resource*);
     Resource* createResourceForLoading(FetchRequest&, const String& charset, const ResourceFactory&);
     void storeResourceTimingInitiatorInformation(Resource*);
     ResourceLoadPriority computeLoadPriority(Resource::Type, const FetchRequest&, ResourcePriority::VisibilityStatus);
 
     Resource* resourceForStaticData(const FetchRequest&, const ResourceFactory&, const SubstituteData&);
+    Resource* resourceForBlockedRequest(const FetchRequest&, const ResourceFactory&);
 
     // RevalidationPolicy enum values are used in UMAs https://crbug.com/579496.
     enum RevalidationPolicy { Use, Revalidate, Reload, Load };
     RevalidationPolicy determineRevalidationPolicy(Resource::Type, const FetchRequest&, Resource* existingResource, bool isStaticData) const;
 
     void moveCachedNonBlockingResourceToBlocking(Resource*, const FetchRequest&);
     void moveResourceLoaderToNonBlocking(ResourceLoader*);
     void removeResourceLoader(ResourceLoader*);
 
     void initializeResourceRequest(ResourceRequest&, Resource::Type, FetchRequest::DeferOption);
@@ skipping 71 matching lines @@
             m_loader->m_allowStaleResources = m_previousState;
     }
 private:
     Member<ResourceFetcher> m_loader;
     bool m_previousState;
 };
 
 } // namespace blink
 
 #endif // ResourceFetcher_h