Make HashTraits<QualifiedName>::emptyValue return a const reference

third_party/WebKit/Source/core/dom/QualifiedName.h

 /*
  * 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
@@ skipping 28 matching lines @@
 
 // This struct is used to pass data between QualifiedName and the
 // QNameTranslator.  For hashing and equality only the QualifiedNameComponents
 // fields are used.
 struct QualifiedNameData {
   DISALLOW_NEW();
   QualifiedNameComponents m_components;
   bool m_isStatic;
 };
 
+CORE_EXPORT extern const class QualifiedName& nullName;
+
 class CORE_EXPORT QualifiedName {
   USING_FAST_MALLOC(QualifiedName);
 
  public:
   class QualifiedNameImpl : public RefCounted<QualifiedNameImpl> {
    public:
     static PassRefPtr<QualifiedNameImpl> create(
         const AtomicString& prefix,
         const AtomicString& localName,
         const AtomicString& namespaceURI,
@@ skipping 94 matching lines @@
   // Uppercased localName, cached for efficiency
   const AtomicString& localNameUpper() const;
 
   String toString() const;
 
   QualifiedNameImpl* impl() const { return m_impl.get(); }
 
   // Init routine for globals
   static void initAndReserveCapacityForSize(unsigned size);
 
-  static const QualifiedName& null();
+  static const QualifiedName& null() { return nullName; }
 
   // The below methods are only for creating static global QNames that need no
   // ref counting.
   static void createStatic(void* targetAddress, StringImpl* name);
   static void createStatic(void* targetAddress,
                            StringImpl* name,
                            const AtomicString& nameNamespace);
 
  private:
   // This constructor is used only to create global/static QNames that don't
@@ skipping 55 matching lines @@
 
 template <>
 struct DefaultHash<blink::QualifiedName> {
   typedef blink::QualifiedNameHash Hash;
 };
 
 template <>
 struct HashTraits<blink::QualifiedName>
     : SimpleClassHashTraits<blink::QualifiedName> {
   static const bool emptyValueIsZero = false;
-  static blink::QualifiedName emptyValue() {
+  static const blink::QualifiedName& emptyValue() {
     return blink::QualifiedName::null();
   }
 };
 }  // namespace WTF
 
 #endif