Use precaching for more data: urls than just images.

Source/core/fetch/ImageResource.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 103 matching lines @@
 
     bool shouldPauseAnimation(const blink::Image*) override;
     void animationAdvanced(const blink::Image*) override;
     void changedInRect(const blink::Image*, const IntRect&) override;
 
 protected:
     bool isSafeToUnlock() const override;
     void destroyDecodedDataIfPossible() override;
 
 private:
-    static void preCacheDataURIImage(const FetchRequest&, ResourceFetcher*);
-
     class ImageResourceFactory : public ResourceFactory {
     public:
         ImageResourceFactory()
             : ResourceFactory(Resource::Image) { }
 
         Resource* create(const ResourceRequest& request, const String&) const override
         {
             return new ImageResource(request);
         }
     };
@@ skipping 18 matching lines @@
 
     RefPtr<blink::Image> m_image;
     bool m_hasDevicePixelRatioHeaderValue;
 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Image);
 
 }
 
 #endif