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

Source/core/dom/StyleElement.cpp

 /*
  * Copyright (C) 2006, 2007 Rob Buis
  * Copyright (C) 2008 Apple, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 106 matching lines @@
 void StyleElement::clearSheet()
 {
     ASSERT(m_sheet);
     m_sheet.release()->clearOwnerNode();
 }
 
 void StyleElement::createSheet(Element* e, const String& text)
 {
     ASSERT(e);
     ASSERT(e->inDocument());
-    Document* document = e->document();
+    Document& document = e->document();
     if (m_sheet) {
         if (m_sheet->isLoading())
-            document->styleSheetCollections()->removePendingSheet(e);
+            document.styleSheetCollections()->removePendingSheet(e);
         clearSheet();
     }
 
     // If type is empty or CSS, this is a CSS style sheet.
     const AtomicString& type = this->type();
-    if (document->contentSecurityPolicy()->allowInlineStyle(e->document()->url(), m_startPosition.m_line) && isCSS(e, type)) {
+    if (document.contentSecurityPolicy()->allowInlineStyle(e->document().url(), m_startPosition.m_line) && isCSS(e, type)) {
         RefPtr<MediaQuerySet> mediaQueries = MediaQuerySet::create(media());
 
         MediaQueryEvaluator screenEval("screen", true);
         MediaQueryEvaluator printEval("print", true);
         if (screenEval.eval(mediaQueries.get()) || printEval.eval(mediaQueries.get())) {
-            document->styleSheetCollections()->addPendingSheet();
+            document.styleSheetCollections()->addPendingSheet();
             m_loading = true;
 
             TextPosition startPosition = m_startPosition == TextPosition::belowRangePosition() ? TextPosition::minimumPosition() : m_startPosition;
-            m_sheet = CSSStyleSheet::createInline(e, KURL(), startPosition, document->inputEncoding());
+            m_sheet = CSSStyleSheet::createInline(e, KURL(), startPosition, document.inputEncoding());
             m_sheet->setMediaQueries(mediaQueries.release());
             m_sheet->setTitle(e->title());
             m_sheet->contents()->parseStringAtPosition(text, startPosition, m_createdByParser);
 
             m_loading = false;
         }
     }
 
     if (m_sheet)
         m_sheet->contents()->checkLoaded();
@@ skipping 16 matching lines @@
     return true;
 }
 
 void StyleElement::startLoadingDynamicSheet(Document* document)
 {
     ASSERT(document);
     document->styleSheetCollections()->addPendingSheet();
 }
 
 }