Make CSSParserContext be garbage collected.

third_party/WebKit/Source/core/html/HTMLContentElement.cpp

 /*
  * Copyright (C) 2011 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.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 45 matching lines @@
 
 DEFINE_TRACE(HTMLContentElement) {
   visitor->trace(m_filter);
   InsertionPoint::trace(visitor);
 }
 
 void HTMLContentElement::parseSelect() {
   DCHECK(m_shouldParseSelect);
 
   m_selectorList = CSSParser::parseSelector(
-      CSSParserContext(document(), nullptr), nullptr, m_select);
+      CSSParserContext::create(document()), nullptr, m_select);
   m_shouldParseSelect = false;
   m_isValidSelector = validateSelect();
   if (!m_isValidSelector)
     m_selectorList = CSSSelectorList();
 }
 
 void HTMLContentElement::parseAttribute(
     const AttributeModificationParams& params) {
   if (params.name == selectAttr) {
     if (ShadowRoot* root = containingShadowRoot()) {
@@ skipping 49 matching lines @@
   for (const CSSSelector* selector = selectorList().first(); selector;
        selector = CSSSelectorList::next(*selector)) {
     context.selector = selector;
     if (checker.match(context))
       return true;
   }
   return false;
 }
 
 }  // namespace blink