0 -> nullptr for UseCounter pointer in CSSParserContext.

third_party/WebKit/Source/core/dom/CSSSelectorWatch.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 131 matching lines @@
     return true;
 }
 
 void CSSSelectorWatch::watchCSSSelectors(const Vector<String>& selectors)
 {
     m_watchedCallbackSelectors.clear();
 
     StylePropertySet* callbackPropertySet = ImmutableStylePropertySet::create(nullptr, 0, UASheetMode);
 
     for (unsigned i = 0; i < selectors.size(); ++i) {
-        CSSSelectorList selectorList = CSSParser::parseSelector(CSSParserContext(UASheetMode, 0), nullptr, selectors[i]);
+        CSSSelectorList selectorList = CSSParser::parseSelector(CSSParserContext(UASheetMode, nullptr), nullptr, selectors[i]);
         if (!selectorList.isValid())
             continue;
 
         // Only accept Compound Selectors, since they're cheaper to match.
         if (!allCompound(selectorList))
             continue;
 
         m_watchedCallbackSelectors.append(StyleRule::create(std::move(selectorList), callbackPropertySet));
     }
     document().styleEngine().watchedSelectorsChanged();
 }
 
 DEFINE_TRACE(CSSSelectorWatch)
 {
     visitor->trace(m_watchedCallbackSelectors);
     visitor->trace(m_document);
     Supplement<Document>::trace(visitor);
 }
 
 } // namespace blink