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

Source/core/svg/SVGViewSpec.cpp

 /*
  * Copyright (C) 2007, 2010 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
@@ skipping 17 matching lines @@
 #include "core/svg/SVGParserUtilities.h"
 
 namespace blink {
 
 SVGViewSpec::SVGViewSpec(SVGSVGElement* contextElement)
     // Note: addToPropertyMap is not needed, as SVGViewSpec do not correspond to an element.
     // Note: We make tear-offs' contextElement the target element of SVGViewSpec.
     // This contextElement will be only used for keeping this alive from the tearoff.
     // SVGSVGElement holds a strong-ref to this SVGViewSpec, so this is kept alive as:
     // AnimatedProperty tearoff -(contextElement)-> SVGSVGElement -(RefPtr)-> SVGViewSpec.
-    : SVGFitToViewBox(contextElement, PropertyMapPolicySkip)
-    , m_contextElement(contextElement)
+    : m_contextElement(contextElement)
     , m_transform(SVGAnimatedTransformList::create(contextElement, SVGNames::transformAttr, SVGTransformList::create()))
 {
+    SVGFitToViewBox::initialize(contextElement, PropertyMapPolicySkip);
+
     ASSERT(m_contextElement);
 
     viewBox()->setReadOnly();
     preserveAspectRatio()->setReadOnly();
     m_transform->setReadOnly();
     // Note: addToPropertyMap is not needed, as SVGViewSpec do not correspond to an element.
 }
 
 void SVGViewSpec::trace(Visitor* visitor)
 {
@@ skipping 159 matching lines @@
             ptr++;
     }
 
     if (ptr >= end || *ptr != ')')
         return false;
 
     return true;
 }
 
 }