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

Source/core/svg/SVGViewElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2007 Rob Buis <buis@kde.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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 
 #include "core/svg/SVGViewElement.h"
 
 namespace blink {
 
 inline SVGViewElement::SVGViewElement(Document& document)
     : SVGElement(SVGNames::viewTag, document)
-    , SVGFitToViewBox(this)
     , m_viewTarget(SVGStaticStringList::create(this, SVGNames::viewTargetAttr))
 {
+    SVGFitToViewBox::initialize(this);
+
     addToPropertyMap(m_viewTarget);
 }
 
 DEFINE_NODE_FACTORY(SVGViewElement)
 
 void SVGViewElement::trace(Visitor* visitor)
 {
     visitor->trace(m_viewTarget);
     SVGElement::trace(visitor);
     SVGFitToViewBox::trace(visitor);
 }
 
 void SVGViewElement::parseAttribute(const QualifiedName& name, const AtomicString& value)
 {
     if (SVGZoomAndPan::parseAttribute(name, value))
         return;
 
     parseAttributeNew(name, value);
 }
 
 } // namespace blink