Allow <use> inside author shadow roots

Source/core/svg/SVGElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2008 Rob Buis <buis@kde.org>
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) 2009 Cameron McCormack <cam@mcc.id.au>
  *
  * 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 218 matching lines @@
 String SVGElement::title() const
 {
     // According to spec, we should not return titles when hovering over root <svg> elements (those
     // <title> elements are the title of the document, not a tooltip) so we instantly return.
     if (isOutermostSVGSVGElement())
         return String();
 
     // Walk up the tree, to find out whether we're inside a <use> shadow tree, to find the right title.
     if (isInShadowTree()) {
         Element* shadowHostElement = toShadowRoot(treeScope().rootNode()).host();
-        // At this time, SVG nodes are not allowed in non-<use> shadow trees, so any shadow root we do
-        // have should be a use. The assert and following test is here to catch future shadow DOM changes
-        // that do enable SVG in a shadow tree.
-        ASSERT(!shadowHostElement || isSVGUseElement(*shadowHostElement));
         if (isSVGUseElement(shadowHostElement)) {
             SVGUseElement& useElement = toSVGUseElement(*shadowHostElement);
 
             // If the <use> title is not empty we found the title to use.
             String useTitle(useElement.title());
             if (!useTitle.isEmpty())
                 return useTitle;
         }
     }
 
@@ skipping 860 matching lines @@
         animatableAttributes.add(SVGNames::zAttr);
     }
 
     if (name == classAttr)
         return true;
 
     return animatableAttributes.contains(name);
 }
 #endif
 }