Use Shadow DOM to display fallback content for images

Source/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. 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
@@ skipping 3804 matching lines @@
     if ((isInline() && !isMarquee()) || !avoidsFloats() || isFloating())
         return false;
 
     // Only auto width objects can possibly shrink to avoid floats.
     return style()->width().isAuto();
 }
 
 static bool isReplacedElement(Node* node)
 {
     // Checkboxes and radioboxes are not isReplaced() nor do they have their own renderer in which to override avoidFloats().
-    return node && node->isElementNode() && toElement(node)->isFormControlElement();
+    return node && node->isElementNode() && (toElement(node)->isFormControlElement() || isHTMLImageElement(toElement(node)));
 }
 
 bool RenderBox::avoidsFloats() const
 {
     return isReplaced() || isReplacedElement(node()) || hasOverflowClip() || isHR() || isLegend() || isWritingModeRoot() || isFlexItemIncludingDeprecated();
 }
 
 InvalidationReason RenderBox::getPaintInvalidationReason(const RenderLayerModelObject& paintInvalidationContainer,
     const LayoutRect& oldBounds, const LayoutPoint& oldLocation, const LayoutRect& newBounds, const LayoutPoint& newLocation)
 {
@@ skipping 687 matching lines @@
     ASSERT(style()->hasBackground() || style()->hasBoxDecorations());
 
     if (m_rareData && m_rareData->m_previousBorderBoxSize.width() != -1)
         return m_rareData->m_previousBorderBoxSize;
 
     // We didn't save the old border box size because it was the same as the size of oldBounds.
     return previousBoundsSize;
 }
 
 } // namespace blink