Introduce few const getters for dom classes

third_party/WebKit/Source/core/css/CSSStyleSheet.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009, 2010, 2012 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 46 matching lines @@
 
     CSSStyleSheet* parentStyleSheet() const override;
     Node* ownerNode() const override { return m_ownerNode; }
     MediaList* media() const override;
     String href() const override;
     String title() const override { return m_title; }
     bool disabled() const override { return m_isDisabled; }
     void setDisabled(bool) override;
 
     CSSRuleList* cssRules();
+    CSSRuleList* maybeCssRules() const;
+
     unsigned insertRule(const String& rule, unsigned index, ExceptionState&);
     unsigned insertRule(const String& rule, ExceptionState&); // Deprecated.
     void deleteRule(unsigned index, ExceptionState&);
 
     // IE Extensions
     CSSRuleList* rules();
     int addRule(const String& selector, const String& style, int index, ExceptionState&);
     int addRule(const String& selector, const String& style, ExceptionState&);
     void removeRule(unsigned index, ExceptionState& exceptionState) { deleteRule(index, exceptionState); }
 
@@ skipping 92 matching lines @@
 {
     if (m_styleSheet)
         m_styleSheet->didMutateRules();
 }
 
 DEFINE_TYPE_CASTS(CSSStyleSheet, StyleSheet, sheet, sheet->isCSSStyleSheet(), sheet.isCSSStyleSheet());
 
 } // namespace blink
 
 #endif