Add WebScopedAXContext to allow a one-time snapshot of accessibility.

Source/core/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 1020 matching lines @@
 {
     if (!layoutObject())
         return IntRect();
     // FIXME: this should probably respect transforms
     return document().view()->contentsToScreen(layoutObject()->absoluteBoundingBoxRectIgnoringTransforms());
 }
 
 const AtomicString& Element::computedRole()
 {
     document().updateLayoutIgnorePendingStylesheets();
-    ScopedAXObjectCache cache(document());
-    return cache->computedRoleForNode(this);
+    RefPtr<ScopedAXObjectCache> cache(adoptRef(new ScopedAXObjectCache(document())));
+    return (*cache)->computedRoleForNode(this);
 }
 
 String Element::computedName()
 {
     document().updateLayoutIgnorePendingStylesheets();
-    ScopedAXObjectCache cache(document());
-    return cache->computedNameForNode(this);
+    RefPtr<ScopedAXObjectCache> cache(adoptRef(new ScopedAXObjectCache(document())));
+    return (*cache)->computedNameForNode(this);
 }
 
 const AtomicString& Element::getAttribute(const AtomicString& localName) const
 {
     if (!elementData())
         return nullAtom;
     synchronizeAttribute(localName);
     if (const Attribute* attribute = elementData()->attributes().find(localName, shouldIgnoreAttributeCase()))
         return attribute->value();
     return nullAtom;
@@ skipping 2436 matching lines @@
 {
 #if ENABLE(OILPAN)
     if (hasRareData())
         visitor->trace(elementRareData());
     visitor->trace(m_elementData);
 #endif
     ContainerNode::trace(visitor);
 }
 
 } // namespace blink