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

Source/core/css/ElementRuleCollector.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 203 matching lines @@
         if (ruleData.selector()->m_match == CSSSelector::Tag && !SelectorChecker::tagMatches(m_context.element(), ruleData.selector()->tagQName()))
             return false;
         SelectorCheckerFastPath selectorCheckerFastPath(ruleData.selector(), m_context.element());
         if (!selectorCheckerFastPath.matchesRightmostAttributeSelector())
             return false;
 
         return selectorCheckerFastPath.matches();
     }
 
     // Slow path.
-    SelectorChecker selectorChecker(document(), m_mode);
+    SelectorChecker selectorChecker(&document(), m_mode);
     SelectorChecker::SelectorCheckingContext context(ruleData.selector(), m_context.element(), SelectorChecker::VisitedMatchEnabled);
     context.elementStyle = m_style.get();
     context.scope = scope;
     context.pseudoId = m_pseudoStyleRequest.pseudoId;
     context.scrollbar = m_pseudoStyleRequest.scrollbar;
     context.scrollbarPart = m_pseudoStyleRequest.scrollbarPart;
     context.behaviorAtBoundary = m_behaviorAtBoundary;
     SelectorChecker::Match match = selectorChecker.match(context, dynamicPseudo, DOMSiblingTraversalStrategy());
     if (match != SelectorChecker::SelectorMatches)
         return false;
@@ skipping 82 matching lines @@
     m_behaviorAtBoundary = SelectorChecker::StaysWithinTreeScope;
     int firstRuleIndex = -1, lastRuleIndex = -1;
     RuleRange ruleRange(firstRuleIndex, lastRuleIndex);
     // FIXME: Verify whether it's ok to ignore CascadeScope here.
     collectMatchingRules(MatchRequest(ruleSet), ruleRange);
 
     return m_matchedRules && !m_matchedRules->isEmpty();
 }
 
 } // namespace WebCore