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

Source/core/html/shadow/PickerIndicatorElement.cpp

 /*
  * Copyright (C) 2012 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 91 matching lines @@
 
 void PickerIndicatorElement::didEndChooser()
 {
     m_chooser.clear();
 }
 
 void PickerIndicatorElement::openPopup()
 {
     if (m_chooser)
         return;
-    if (!document()->page())
+    if (!document().page())
         return;
     if (!m_pickerIndicatorOwner)
         return;
     DateTimeChooserParameters parameters;
     if (!m_pickerIndicatorOwner->setupDateTimeChooserParameters(parameters))
         return;
-    m_chooser = document()->page()->chrome().openDateTimeChooser(this, parameters);
+    m_chooser = document().page()->chrome().openDateTimeChooser(this, parameters);
 }
 
 void PickerIndicatorElement::closePopup()
 {
     if (!m_chooser)
         return;
     m_chooser->endChooser();
 }
 
 void PickerIndicatorElement::detach(const AttachContext& context)
 {
     closePopup();
     HTMLDivElement::detach(context);
 }
 
 bool PickerIndicatorElement::isPickerIndicatorElement() const
 {
     return true;
 }
 
 }
 
 #endif