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

Source/core/html/HTMLMetaElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2010 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.
@@ skipping 59 matching lines @@
 void HTMLMetaElement::process()
 {
     if (!inDocument())
         return;
 
     const AtomicString& contentValue = fastGetAttribute(contentAttr);
     if (contentValue.isNull())
         return;
 
     if (equalIgnoringCase(name(), "viewport"))
-        document()->processViewport(contentValue, ViewportArguments::ViewportMeta);
+        document().processViewport(contentValue, ViewportArguments::ViewportMeta);
     else if (equalIgnoringCase(name(), "referrer"))
-        document()->processReferrerPolicy(contentValue);
+        document().processReferrerPolicy(contentValue);
     else if (equalIgnoringCase(name(), "handheldfriendly") && equalIgnoringCase(contentValue, "true"))
-        document()->processViewport("width=device-width", ViewportArguments::HandheldFriendlyMeta);
+        document().processViewport("width=device-width", ViewportArguments::HandheldFriendlyMeta);
     else if (equalIgnoringCase(name(), "mobileoptimized"))
-        document()->processViewport("width=device-width, initial-scale=1", ViewportArguments::MobileOptimizedMeta);
+        document().processViewport("width=device-width, initial-scale=1", ViewportArguments::MobileOptimizedMeta);
 
     // Get the document to process the tag, but only if we're actually part of DOM tree (changing a meta tag while
     // it's not in the tree shouldn't have any effect on the document)
     const AtomicString& httpEquivValue = fastGetAttribute(http_equivAttr);
     if (!httpEquivValue.isNull())
-        document()->processHttpEquiv(httpEquivValue, contentValue);
+        document().processHttpEquiv(httpEquivValue, contentValue);
 }
 
 String HTMLMetaElement::content() const
 {
     return getAttribute(contentAttr);
 }
 
 String HTMLMetaElement::httpEquiv() const
 {
     return getAttribute(http_equivAttr);
 }
 
 String HTMLMetaElement::name() const
 {
     return getNameAttribute();
 }
 
 }