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

Source/core/dom/DocumentEventQueue.cpp

 /*
  * Copyright (C) 2010 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 62 matching lines @@
     ASSERT_UNUSED(wasAdded, wasAdded); // It should not have already been in the list.
 
     if (!m_pendingEventTimer->isActive())
         m_pendingEventTimer->startOneShot(0);
 
     return true;
 }
 
 void DocumentEventQueue::enqueueOrDispatchScrollEvent(PassRefPtr<Node> target, ScrollEventTargetType targetType)
 {
-    if (!target->document()->hasListenerType(Document::SCROLL_LISTENER))
+    if (!target->document().hasListenerType(Document::SCROLL_LISTENER))
         return;
 
     // Per the W3C CSSOM View Module, scroll events fired at the document should bubble, others should not.
     RefPtr<Event> scrollEvent = targetType == ScrollEventDocumentTarget ? Event::createBubble(eventNames().scrollEvent) : Event::create(eventNames().scrollEvent);
 
     if (!m_nodesWithQueuedScrollEvents.add(target.get()).isNewEntry)
         return;
 
     scrollEvent->setTarget(target);
     enqueueEvent(scrollEvent.release());
@@ skipping 44 matching lines @@
 void DocumentEventQueue::dispatchEvent(PassRefPtr<Event> event)
 {
     EventTarget* eventTarget = event->target();
     if (eventTarget->toDOMWindow())
         eventTarget->toDOMWindow()->dispatchEvent(event, 0);
     else
         eventTarget->dispatchEvent(event);
 }
 
 }