Revert 146726 "AXObjectCache gets recreated during document tear..."

Source/WebCore/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 866 matching lines @@
     shouldInvalidateStyle |= testShouldInvalidateStyle && styleResolver->hasSelectorForAttribute(name.localName());
 
     invalidateNodeListCachesInAncestors(&name, this);
 
     // If there is currently no StyleResolver, we can't be sure that this attribute change won't affect style.
     shouldInvalidateStyle |= !styleResolver;
 
     if (shouldInvalidateStyle)
         setNeedsStyleRecalc();
 
-    if (AXObjectCache* cache = document()->existingAXObjectCache())
-        cache->handleAttributeChanged(name, this);
+    if (AXObjectCache::accessibilityEnabled())
+        document()->axObjectCache()->handleAttributeChanged(name, this);
 }
 
 inline void Element::attributeChangedFromParserOrByCloning(const QualifiedName& name, const AtomicString& newValue)
 {
 #if ENABLE(CUSTOM_ELEMENTS)
     if (name == isAttr) {
         if (CustomElementRegistry* registry = document()->registry())
             registry->didGiveTypeExtension(this);
     }
 #endif
@@ skipping 2242 matching lines @@
     return 0;
 }
 
 Attribute* UniqueElementData::attributeItem(unsigned index)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(index < length());
     return &m_attributeVector.at(index);
 }
 
 } // namespace WebCore