Use Shadow DOM to display fallback content for images

Source/core/rendering/RenderImage.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2006 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2009, 2010, 2011 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
@@ skipping 33 matching lines @@
     virtual void destroy() override;
 
     static RenderImage* createAnonymous(Document*);
 
     void setImageResource(PassOwnPtr<RenderImageResource>);
 
     RenderImageResource* imageResource() { return m_imageResource.get(); }
     const RenderImageResource* imageResource() const { return m_imageResource.get(); }
     ImageResource* cachedImage() const { return m_imageResource ? m_imageResource->cachedImage() : 0; }
 
-    bool setImageSizeForAltText(ImageResource* newImage = 0);
-
-    void updateAltText();
-
     HTMLMapElement* imageMap() const;
     void areaElementFocusChanged(HTMLAreaElement*);
 
     void setIsGeneratedContent(bool generated = true) { m_isGeneratedContent = generated; }
 
     bool isGeneratedContent() const { return m_isGeneratedContent; }
 
-    String altText() const { return m_altText; }
-
     inline void setImageDevicePixelRatio(float factor) { m_imageDevicePixelRatio = factor; }
     float imageDevicePixelRatio() const { return m_imageDevicePixelRatio; }
 
     virtual void intrinsicSizeChanged() override
     {
         if (m_imageResource)
             imageChanged(m_imageResource->imagePtr());
     }
 
 protected:
@@ skipping 22 matching lines @@
 
     virtual bool backgroundShouldAlwaysBeClipped() const override { return true; }
 
     virtual LayoutUnit minimumReplacedHeight() const override;
 
     virtual void notifyFinished(Resource*) override final;
     virtual bool nodeAtPoint(const HitTestRequest&, HitTestResult&, const HitTestLocation& locationInContainer, const LayoutPoint& accumulatedOffset, HitTestAction) override final;
 
     virtual bool boxShadowShouldBeAppliedToBackground(BackgroundBleedAvoidance, InlineFlowBox*) const override final;
 
-    IntSize imageSizeForError(ImageResource*) const;
-    void paintInvalidationOrMarkForLayout(bool imageSizeChanged, const IntRect* = 0);
+    void repaintOrMarkForLayout(const IntRect* = 0);
     void updateIntrinsicSizeIfNeeded(const LayoutSize&);
     // Update the size of the image to be rendered. Object-fit may cause this to be different from the CSS box's content rect.
     void updateInnerContentRect();
 
     // Text to display as long as the image isn't available.
-    String m_altText;
     OwnPtr<RenderImageResource> m_imageResource;
     bool m_didIncrementVisuallyNonEmptyPixelCount;
     bool m_isGeneratedContent;
     float m_imageDevicePixelRatio;
 
     friend class RenderImageScaleObserver;
 };
 
 DEFINE_RENDER_OBJECT_TYPE_CASTS(RenderImage, isRenderImage());
 
 } // namespace blink
 
 #endif // RenderImage_h