Have HashMap<KeyType, AtomicString>::get() return a const reference

Source/core/html/HTMLElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2011 Motorola Mobility. 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
@@ skipping 187 matching lines @@
     } else if (name.matches(XMLNames::langAttr))
         mapLanguageAttributeToLocale(value, style);
     else if (name == langAttr) {
         // xml:lang has a higher priority than lang.
         if (!fastHasAttribute(XMLNames::langAttr))
             mapLanguageAttributeToLocale(value, style);
     } else
         Element::collectStyleForPresentationAttribute(name, value, style);
 }
 
-AtomicString HTMLElement::eventNameForAttributeName(const QualifiedName& attrName) const
+const AtomicString& HTMLElement::eventNameForAttributeName(const QualifiedName& attrName) const
 {
     if (!attrName.namespaceURI().isNull())
-        return AtomicString();
+        return nullAtom;
 
     typedef HashMap<AtomicString, AtomicString> StringToStringMap;
     DEFINE_STATIC_LOCAL(StringToStringMap, attributeNameToEventNameMap, ());
     if (!attributeNameToEventNameMap.size()) {
         attributeNameToEventNameMap.set(onanimationstartAttr.localName(), EventTypeNames::animationstart);
         attributeNameToEventNameMap.set(onanimationiterationAttr.localName(), EventTypeNames::animationiteration);
         attributeNameToEventNameMap.set(onanimationendAttr.localName(), EventTypeNames::animationend);
         attributeNameToEventNameMap.set(oncancelAttr.localName(), EventTypeNames::cancel);
         attributeNameToEventNameMap.set(onclickAttr.localName(), EventTypeNames::click);
         attributeNameToEventNameMap.set(oncloseAttr.localName(), EventTypeNames::close);
@@ skipping 91 matching lines @@
             if (treeScope().adjustedFocusedElement() == this) {
                 // We might want to call blur(), but it's dangerous to dispatch
                 // events here.
                 document().setNeedsFocusedElementCheck();
             }
         } else if (parseHTMLInteger(value, tabindex)) {
             // Clamp tabindex to the range of 'short' to match Firefox's behavior.
             setTabIndexExplicitly(max(static_cast<int>(std::numeric_limits<short>::min()), min(tabindex, static_cast<int>(std::numeric_limits<short>::max()))));
         }
     } else {
-        AtomicString eventName = eventNameForAttributeName(name);
+        const AtomicString& eventName = eventNameForAttributeName(name);
         if (!eventName.isNull())
             setAttributeEventListener(eventName, createAttributeEventListener(this, name, value));
     }
 }
 
 PassRefPtr<DocumentFragment> HTMLElement::textToFragment(const String& text, ExceptionState& exceptionState)
 {
     RefPtr<DocumentFragment> fragment = DocumentFragment::create(document());
     unsigned int i, length = text.length();
     UChar c = 0;
@@ skipping 742 matching lines @@
 #ifndef NDEBUG
 
 // For use in the debugger
 void dumpInnerHTML(WebCore::HTMLElement*);
 
 void dumpInnerHTML(WebCore::HTMLElement* element)
 {
     printf("%s\n", element->innerHTML().ascii().data());
 }
 #endif