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

Source/core/accessibility/AccessibilityListBoxOption.cpp

 /*
  * Copyright (C) 2008 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
@@ skipping 88 matching lines @@
         return rect;
 
     HTMLSelectElement* listBoxParentNode = listBoxOptionParentNode();
     if (!listBoxParentNode)
         return rect;
 
     RenderObject* listBoxRenderer = listBoxParentNode->renderer();
     if (!listBoxRenderer)
         return rect;
 
-    LayoutRect parentRect = listBoxRenderer->document()->axObjectCache()->getOrCreate(listBoxRenderer)->elementRect();
+    LayoutRect parentRect = listBoxRenderer->document().axObjectCache()->getOrCreate(listBoxRenderer)->elementRect();
     int index = listBoxOptionIndex();
     if (index != -1)
         rect = toRenderListBox(listBoxRenderer)->itemBoundingBoxRect(parentRect.location(), index);
 
     return rect;
 }
 
 bool AccessibilityListBoxOption::computeAccessibilityIsIgnored() const
 {
     if (!m_optionElement)
@@ skipping 45 matching lines @@
 {
     return m_optionElement;
 }
 
 AccessibilityObject* AccessibilityListBoxOption::parentObject() const
 {
     HTMLSelectElement* parentNode = listBoxOptionParentNode();
     if (!parentNode)
         return 0;
 
-    return m_optionElement->document()->axObjectCache()->getOrCreate(parentNode);
+    return m_optionElement->document().axObjectCache()->getOrCreate(parentNode);
 }
 
 void AccessibilityListBoxOption::setSelected(bool selected)
 {
     HTMLSelectElement* selectElement = listBoxOptionParentNode();
     if (!selectElement)
         return;
 
     if (!canSetSelectedAttribute())
         return;
@@ skipping 33 matching lines @@
     const Vector<HTMLElement*>& listItems = selectElement->listItems();
     unsigned length = listItems.size();
     for (unsigned i = 0; i < length; i++)
         if (listItems[i] == m_optionElement)
             return i;
 
     return -1;
 }
 
 } // namespace WebCore