Oilpan: disable conservative GCs during initial GC mixin construction.

Source/core/svg/SVGAElement.h

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@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 13 matching lines @@
 
 #include "core/svg/SVGAnimatedBoolean.h"
 #include "core/svg/SVGGraphicsElement.h"
 #include "core/svg/SVGURIReference.h"
 
 namespace blink {
 
 class SVGAElement final : public SVGGraphicsElement,
                           public SVGURIReference {
     DEFINE_WRAPPERTYPEINFO();
-    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(SVGAElement);
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN_NESTED(SVGAElement, SVGGraphicsElement);
 public:
     DECLARE_NODE_FACTORY(SVGAElement);
     SVGAnimatedString* svgTarget() { return m_svgTarget.get(); }
 
     DECLARE_VIRTUAL_TRACE();
 
 private:
     explicit SVGAElement(Document&);
 
     virtual String title() const override;
@@ skipping 18 matching lines @@
 
     virtual bool willRespondToMouseClickEvents() override;
 
     RefPtrWillBeMember<SVGAnimatedString> m_svgTarget;
     bool m_wasFocusedByMouse;
 };
 
 } // namespace blink
 
 #endif // SVGAElement_h