Remove raw pointer member to AXObjectCache

Source/web/WebAXObject.cpp

Index: Source/web/WebAXObject.cpp
diff --git a/Source/web/WebAXObject.cpp b/Source/web/WebAXObject.cpp
index 5ae489c68cfa1657ae88bd02a437228fd93caef2..d65dafc4464844dbb7f365f2b77697dc3d27d293 100644
--- a/Source/web/WebAXObject.cpp
+++ b/Source/web/WebAXObject.cpp
@@ -76,15 +76,10 @@ static bool isLayoutClean(Document* document)
 #endif
 
 WebScopedAXContext::WebScopedAXContext(WebDocument& rootDocument)
-    : m_private(adoptRef(new ScopedAXObjectCache(*rootDocument.unwrap<Document>())))
+    : m_private(ScopedAXObjectCache::create(*rootDocument.unwrap<Document>()))
 {
 }
 
-WebScopedAXContext::~WebScopedAXContext()
-{
-    m_private.reset();
-}
-
 WebAXObject WebScopedAXContext::root() const
 {
     return WebAXObject(static_cast<AXObjectCacheImpl*>(m_private->get())->root());