Initialize GC mixin bases only when leftmost vtable has been initialized.

Source/core/svg/SVGFEImageElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2010 Dirk Schulze <krit@webkit.org>
  *
  * 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 17 matching lines @@
 #include "core/fetch/ResourceFetcher.h"
 #include "core/svg/SVGDocumentExtensions.h"
 #include "core/svg/SVGPreserveAspectRatio.h"
 #include "core/svg/graphics/filters/SVGFEImage.h"
 #include "platform/graphics/Image.h"
 
 namespace blink {
 
 inline SVGFEImageElement::SVGFEImageElement(Document& document)
     : SVGFilterPrimitiveStandardAttributes(SVGNames::feImageTag, document)
-    , SVGURIReference(this)
     , m_preserveAspectRatio(SVGAnimatedPreserveAspectRatio::create(this, SVGNames::preserveAspectRatioAttr, SVGPreserveAspectRatio::create()))
 {
+    SVGURIReference::initialize(this);
+
     addToPropertyMap(m_preserveAspectRatio);
 }
 
 DEFINE_NODE_FACTORY(SVGFEImageElement)
 
 SVGFEImageElement::~SVGFEImageElement()
 {
 #if ENABLE(OILPAN)
     if (m_cachedImage) {
         m_cachedImage->removeClient(this);
@@ skipping 129 matching lines @@
 }
 
 PassRefPtrWillBeRawPtr<FilterEffect> SVGFEImageElement::build(SVGFilterBuilder*, Filter* filter)
 {
     if (m_cachedImage)
         return FEImage::createWithImage(filter, m_cachedImage->imageForRenderer(renderer()), m_preserveAspectRatio->currentValue());
     return FEImage::createWithIRIReference(filter, treeScope(), hrefString(), m_preserveAspectRatio->currentValue());
 }
 
 }