Use precaching for more data: urls than just images.

Source/core/fetch/RawResource.h

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller <mueller@kde.org>
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007 Apple Inc. All rights reserved.
 
     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 49 matching lines @@
     class RawResourceFactory : public ResourceFactory {
     public:
         RawResourceFactory(Resource::Type type)
             : ResourceFactory(type) { }
 
         Resource* create(const ResourceRequest& request, const String& charset) const override
         {
             return new RawResource(request, m_type);
         }
     };
-    static void preCacheSubstituteDataForMainResource(const FetchRequest&, ResourceFetcher*, const SubstituteData&);
 
     void didAddClient(ResourceClient*) override;
     void appendData(const char*, unsigned) override;
 
     bool shouldIgnoreHTTPStatusCodeErrors() const override { return true; }
 
     void willFollowRedirect(ResourceRequest&, const ResourceResponse&) override;
     void updateRequest(const ResourceRequest&) override;
     void responseReceived(const ResourceResponse&, PassOwnPtr<WebDataConsumerHandle>) override;
     void setSerializedCachedMetadata(const char*, size_t) override;
@@ skipping 27 matching lines @@
     virtual void dataReceived(Resource*, const char* /* data */, unsigned /* length */) { }
     virtual void redirectReceived(Resource*, ResourceRequest&, const ResourceResponse&) { }
     virtual void updateRequest(Resource*, const ResourceRequest&) { }
     virtual void dataDownloaded(Resource*, int) { }
     virtual void didReceiveResourceTiming(Resource*, const ResourceTimingInfo&) { }
 };
 
 }
 
 #endif // RawResource_h