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

Source/core/page/animation/ImplicitAnimation.cpp

 /*
  * Copyright (C) 2007 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 43 matching lines @@
 
 ImplicitAnimation::~ImplicitAnimation()
 {
     // // Make sure to tell the renderer that we are ending. This will make sure any accelerated animations are removed.
     if (!postActive())
         endAnimation();
 }
 
 bool ImplicitAnimation::shouldSendEventForListener(Document::ListenerType inListenerType) const
 {
-    return m_object->document()->hasListenerType(inListenerType);
+    return m_object->document().hasListenerType(inListenerType);
 }
 
 void ImplicitAnimation::animate(CompositeAnimation*, RenderObject*, const RenderStyle*, RenderStyle* targetStyle, RefPtr<RenderStyle>& animatedStyle)
 {
     // If we get this far and the animation is done, it means we are cleaning up a just finished animation.
     // So just return. Everything is already all cleaned up.
     if (postActive())
         return;
 
     // Reset to start the transition if we are new
@@ skipping 207 matching lines @@
     // only need service at the end of the transition.
     if (CSSPropertyAnimation::animationOfPropertyIsAccelerated(m_animatingProperty) && isAccelerated()) {
         bool isLooping;
         getTimeToNextEvent(t, isLooping);
     }
 
     return t;
 }
 
 } // namespace WebCore