Improve DEFINE_STATIC_LOCAL()'s handling of Blink GCed objects.

third_party/WebKit/Source/core/svg/SVGElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2008 Rob Buis <buis@kde.org>
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) 2009 Cameron McCormack <cam@mcc.id.au>
  *
  * 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
@@ skipping 520 matching lines @@
     if (!hasSVGRareData())
         return;
 
     HeapHashSet<WeakMember<SVGElement>>& instances = svgRareData()->elementInstances();
 
     instances.remove(instance);
 }
 
 static HeapHashSet<WeakMember<SVGElement>>& emptyInstances()
 {
-    DEFINE_STATIC_LOCAL(Persistent<HeapHashSet<WeakMember<SVGElement>>>, emptyInstances, (new HeapHashSet<WeakMember<SVGElement>>()));
-    return *emptyInstances;
+    DEFINE_STATIC_LOCAL(HeapHashSet<WeakMember<SVGElement>>, emptyInstances, (new HeapHashSet<WeakMember<SVGElement>>));
+    return emptyInstances;
 }
 
 const HeapHashSet<WeakMember<SVGElement>>& SVGElement::instancesForElement() const
 {
     if (!hasSVGRareData())
         return emptyInstances();
     return svgRareData()->elementInstances();
 }
 
 void SVGElement::setCursorElement(SVGCursorElement* cursorElement)
@@ skipping 667 matching lines @@
     Element::trace(visitor);
 }
 
 const AtomicString& SVGElement::eventParameterName()
 {
     DEFINE_STATIC_LOCAL(const AtomicString, evtString, ("evt"));
     return evtString;
 }
 
 } // namespace blink