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

third_party/WebKit/Source/core/xml/XPathValue.cpp

 /*
  * Copyright 2005 Frerich Raabe <raabe@kde.org>
  * Copyright (C) 2006 Apple Computer, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 35 matching lines @@
 {
     visitor->trace(m_data);
 }
 
 const NodeSet& Value::toNodeSet(EvaluationContext* context) const
 {
     if (!isNodeSet() && context)
         context->hadTypeConversionError = true;
 
     if (!m_data) {
-        DEFINE_STATIC_LOCAL(Persistent<NodeSet>, emptyNodeSet, (NodeSet::create()));
-        return *emptyNodeSet;
+        DEFINE_STATIC_LOCAL(NodeSet, emptyNodeSet, (NodeSet::create()));
+        return emptyNodeSet;
     }
 
     return m_data->nodeSet();
 }
 
 NodeSet& Value::modifiableNodeSet(EvaluationContext& context)
 {
     if (!isNodeSet())
         context.hadTypeConversionError = true;
 
@@ skipping 71 matching lines @@
         return String::number(m_number);
     case BooleanValue:
         return m_bool ? "true" : "false";
     }
     ASSERT_NOT_REACHED();
     return String();
 }
 
 } // namespace XPath
 } // namespace blink