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

Source/core/svg/SVGCursorElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 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,
@@ skipping 11 matching lines @@
 
 #include "core/svg/SVGCursorElement.h"
 
 #include "core/SVGNames.h"
 #include "core/XLinkNames.h"
 
 namespace blink {
 
 inline SVGCursorElement::SVGCursorElement(Document& document)
     : SVGElement(SVGNames::cursorTag, document)
-    , SVGTests(this)
-    , SVGURIReference(this)
     , m_x(SVGAnimatedLength::create(this, SVGNames::xAttr, SVGLength::create(LengthModeWidth), AllowNegativeLengths))
     , m_y(SVGAnimatedLength::create(this, SVGNames::yAttr, SVGLength::create(LengthModeHeight), AllowNegativeLengths))
 {
+    SVGTests::initialize(this);
+    SVGURIReference::initialize(this);
+
     addToPropertyMap(m_x);
     addToPropertyMap(m_y);
 }
 
 DEFINE_NODE_FACTORY(SVGCursorElement)
 
 SVGCursorElement::~SVGCursorElement()
 {
     // The below teardown is all handled by weak pointer processing in oilpan.
 #if !ENABLE(OILPAN)
@@ skipping 61 matching lines @@
     visitor->trace(m_x);
     visitor->trace(m_y);
     visitor->trace(m_clients);
 #endif
     SVGElement::trace(visitor);
     SVGTests::trace(visitor);
     SVGURIReference::trace(visitor);
 }
 
 } // namespace blink