Cleanup: Start using toFoo methods as part of newly adopted coding guideline.

Source/core/css/StyleRule.h

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2006, 2008, 2012, 2013 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 110 matching lines @@
     RefPtr<StylePropertySet> m_properties;
     CSSSelectorList m_selectorList;
 };
 
 inline const StyleRule* toStyleRule(const StyleRuleBase* rule)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isStyleRule());
     return static_cast<const StyleRule*>(rule);
 }
 
+inline StyleRule* toStyleRule(StyleRuleBase* rule)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!rule || rule->isStyleRule());
+    return static_cast<StyleRule*>(rule);
+}
+
+void toStyleRule(const StyleRule*);
+
 class StyleRuleFontFace : public StyleRuleBase {
 public:
     static PassRefPtr<StyleRuleFontFace> create() { return adoptRef(new StyleRuleFontFace); }
 
     ~StyleRuleFontFace();
 
     const StylePropertySet* properties() const { return m_properties.get(); }
     MutableStylePropertySet* mutableProperties();
 
     void setProperties(PassRefPtr<StylePropertySet>);
@@ skipping 172 matching lines @@
     StyleRuleFilter(const String&);
     StyleRuleFilter(const StyleRuleFilter&);
 
     String m_filterName;
     RefPtr<StylePropertySet> m_properties;
 };
 
 } // namespace WebCore
 
 #endif // StyleRule_h