Refactor ScopedAXObjectCache to remove ref count

Source/modules/accessibility/AXObjectCacheImpl.h

 /*
  * Copyright (C) 2014, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 39 matching lines @@
     AXID axID;
     Node* node;
     int offset;
     EAffinity affinity;
 };
 
 // This class should only be used from inside the accessibility directory.
 class MODULES_EXPORT AXObjectCacheImpl : public AXObjectCache {
     WTF_MAKE_NONCOPYABLE(AXObjectCacheImpl); WTF_MAKE_FAST_ALLOCATED(AXObjectCacheImpl);
 public:
-    static AXObjectCache* create(Document&);
+    static PassOwnPtr<AXObjectCache> create(Document&);
 
     explicit AXObjectCacheImpl(Document&);
     ~AXObjectCacheImpl();
 
     AXObject* focusedUIElementForPage(const Page*);
 
     virtual void selectionChanged(Node*) override;
     virtual void childrenChanged(Node*) override;
     virtual void childrenChanged(LayoutObject*) override;
     virtual void checkedStateChanged(Node*) override;
@@ skipping 134 matching lines @@
 // This is the only subclass of AXObjectCache.
 DEFINE_TYPE_CASTS(AXObjectCacheImpl, AXObjectCache, cache, true, true);
 
 bool nodeHasRole(Node*, const String& role);
 // This will let you know if aria-hidden was explicitly set to false.
 bool isNodeAriaVisible(Node*);
 
 }
 
 #endif