Have Node::document() return a reference instead of a pointer

Source/core/accessibility/AccessibilityMenuList.cpp

 /*
  * Copyright (C) 2010 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 38 matching lines @@
         menuList->hidePopup();
     else
         menuList->showPopup();
     return true;
 }
 
 void AccessibilityMenuList::addChildren()
 {
     m_haveChildren = true;
 
-    AXObjectCache* cache = m_renderer->document()->axObjectCache();
+    AXObjectCache* cache = m_renderer->document().axObjectCache();
 
     AccessibilityObject* list = cache->getOrCreate(MenuListPopupRole);
     if (!list)
         return;
 
     static_cast<AccessibilityMockObject*>(list)->setParent(this);
     if (list->accessibilityIsIgnored()) {
         cache->remove(list->axObjectID());
         return;
     }
@@ skipping 20 matching lines @@
 bool AccessibilityMenuList::canSetFocusAttribute() const
 {
     if (!node())
         return false;
 
     return !toElement(node())->isDisabledFormControl();
 }
 
 void AccessibilityMenuList::didUpdateActiveOption(int optionIndex)
 {
-    RefPtr<Document> document = m_renderer->document();
+    RefPtr<Document> document = &m_renderer->document();
     AXObjectCache* cache = document->axObjectCache();
 
     const AccessibilityChildrenVector& childObjects = children();
     if (!childObjects.isEmpty()) {
         ASSERT(childObjects.size() == 1);
         ASSERT(childObjects[0]->isMenuListPopup());
 
         if (childObjects[0]->isMenuListPopup()) {
             if (AccessibilityMenuListPopup* popup = static_cast<AccessibilityMenuListPopup*>(childObjects[0].get()))
                 popup->didUpdateActiveOption(optionIndex);
         }
     }
 
     cache->postNotification(this, document.get(), AXObjectCache::AXMenuListValueChanged, true, PostSynchronously);
 }
 
 } // namespace WebCore