[oilpan]: Avoid refcounting QualifiedName's nullQName when tracing.

Source/core/dom/QualifiedName.cpp

 /*
  * Copyright (C) 2005, 2006, 2009 Apple Inc. All rights reserved.
  *
  * 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "config.h"
 
 #ifdef SKIP_STATIC_CONSTRUCTORS_ON_GCC
 #define WEBCORE_QUALIFIEDNAME_HIDE_GLOBALS 1
-#else
-#define QNAME_DEFAULT_CONSTRUCTOR
 #endif
 
 #include "HTMLNames.h"
 #include "SVGNames.h"
 #include "XLinkNames.h"
 #include "XMLNSNames.h"
 #include "XMLNames.h"
 #include "core/dom/QualifiedName.h"
 #include "wtf/Assertions.h"
 #include "wtf/HashSet.h"
@@ skipping 71 matching lines @@
 }
 
 const QualifiedName& nullQName()
 {
     DEFINE_STATIC_LOCAL(QualifiedName, nullName, (nullAtom, nullAtom, nullAtom));
     return nullName;
 }
 
 const AtomicString& QualifiedName::localNameUpper() const
 {
+    if (!m_impl)
+        return nullAtom;
     if (!m_impl->m_localNameUpper)
         m_impl->m_localNameUpper = m_impl->m_localName.upper();
     return m_impl->m_localNameUpper;
 }
 
 unsigned QualifiedName::QualifiedNameImpl::computeHash() const
 {
     QualifiedNameComponents components = { m_prefix.impl(), m_localName.impl(), m_namespace.impl() };
     return hashComponents(components);
 }
 
 void createQualifiedName(void* targetAddress, StringImpl* name, const AtomicString& nameNamespace)
 {
     new (targetAddress) QualifiedName(nullAtom, AtomicString(name), nameNamespace);
 }
 
 void createQualifiedName(void* targetAddress, StringImpl* name)
 {
     new (targetAddress) QualifiedName(nullAtom, AtomicString(name), nullAtom);
 }
 
 }