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

Source/core/svg/SVGGraphicsElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006 Rob Buis <buis@kde.org>
  * Copyright (C) 2014 Google, Inc.
  *
  * 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 16 matching lines @@
 #include "core/css/resolver/StyleResolver.h"
 #include "core/rendering/svg/RenderSVGPath.h"
 #include "core/rendering/svg/SVGPathData.h"
 #include "core/svg/SVGElementRareData.h"
 #include "platform/transforms/AffineTransform.h"
 
 namespace blink {
 
 SVGGraphicsElement::SVGGraphicsElement(const QualifiedName& tagName, Document& document, ConstructionType constructionType)
     : SVGElement(tagName, document, constructionType)
-    , SVGTests(this)
     , m_transform(SVGAnimatedTransformList::create(this, SVGNames::transformAttr, SVGTransformList::create()))
 {
+    SVGTests::initialize(this);
+
     addToPropertyMap(m_transform);
 }
 
 SVGGraphicsElement::~SVGGraphicsElement()
 {
 }
 
 void SVGGraphicsElement::trace(Visitor* visitor)
 {
     visitor->trace(m_transform);
@@ skipping 222 matching lines @@
     return new RenderSVGPath(this);
 }
 
 void SVGGraphicsElement::toClipPath(Path& path)
 {
     updatePathFromGraphicsElement(this, path);
     path.transform(calculateAnimatedLocalTransform());
 }
 
 }