Use Shadow DOM to display fallback content for 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 42 matching lines @@
     ImageResource(const ResourceRequest&, blink::Image*);
     virtual ~ImageResource();
 
     virtual void load(ResourceFetcher*, const ResourceLoaderOptions&) override;
 
     blink::Image* image(); // Returns the nullImage() if the image is not available yet.
     blink::Image* imageForRenderer(const RenderObject*); // Returns the nullImage() if the image is not available yet.
     bool hasImage() const { return m_image.get(); }
     bool currentFrameKnownToBeOpaque(const RenderObject*); // Side effect: ensures decoded image is in cache, therefore should only be called when about to draw the image.
 
-    static std::pair<blink::Image*, float> brokenImage(float deviceScaleFactor); // Returns an image and the image's resolution scale factor.
-    bool willPaintBrokenImage() const;
-
     bool canRender(const RenderObject& renderer, float multiplier) { return !errorOccurred() && !imageSizeForRenderer(&renderer, multiplier).isEmpty(); }
 
     void setContainerSizeForRenderer(const ImageResourceClient*, const IntSize&, float);
     bool usesImageContainerSize() const;
     bool imageHasRelativeWidth() const;
     bool imageHasRelativeHeight() const;
     // The device pixel ratio we got from the server for this image, or 1.0.
     float devicePixelRatioHeaderValue() const { return m_devicePixelRatioHeaderValue; }
     bool hasDevicePixelRatioHeaderValue() const { return m_hasDevicePixelRatioHeaderValue; }
 
@@ skipping 58 matching lines @@
     OwnPtr<SVGImageCache> m_svgImageCache;
     bool m_loadingMultipartContent;
     bool m_hasDevicePixelRatioHeaderValue;
 };
 
 DEFINE_RESOURCE_TYPE_CASTS(Image);
 
 }
 
 #endif