0 -> nullptr for UseCounter pointer in CSSParserContext.

third_party/WebKit/Source/core/css/CSSStyleRule.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * (C) 2002-2003 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2002, 2005, 2006, 2008, 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.
  *
@@ skipping 66 matching lines @@
 
     ASSERT(!selectorTextCache().contains(this));
     String text = generateSelectorText();
     selectorTextCache().set(this, text);
     setHasCachedSelectorText(true);
     return text;
 }
 
 void CSSStyleRule::setSelectorText(const String& selectorText)
 {
-    CSSParserContext context(parserContext(), 0);
+    CSSParserContext context(parserContext(), nullptr);
     CSSSelectorList selectorList = CSSParser::parseSelector(context, parentStyleSheet() ? parentStyleSheet()->contents() : nullptr, selectorText);
     if (!selectorList.isValid())
         return;
 
     CSSStyleSheet::RuleMutationScope mutationScope(this);
 
     m_styleRule->wrapperAdoptSelectorList(std::move(selectorList));
 
     if (hasCachedSelectorText()) {
         selectorTextCache().remove(this);
@@ skipping 30 matching lines @@
 }
 
 DEFINE_TRACE_WRAPPERS(CSSStyleRule)
 {
     visitor->traceWrappers(parentRule());
     visitor->traceWrappers(parentStyleSheet());
     CSSRule::traceWrappers(visitor);
 }
 
 } // namespace blink