Make CSSParserContext be garbage collected.

third_party/WebKit/Source/core/css/parser/CSSSelectorParser.h

Index: third_party/WebKit/Source/core/css/parser/CSSSelectorParser.h
diff --git a/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.h b/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.h
index 8c9c3576c5e5a427f1bf2e558605b2617ce8e325..216e262fe209d9bbb3dd2c185229e29c11b16a16 100644
--- a/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.h
+++ b/third_party/WebKit/Source/core/css/parser/CSSSelectorParser.h
@@ -23,13 +23,13 @@ class CORE_EXPORT CSSSelectorParser {
 
  public:
   static CSSSelectorList parseSelector(CSSParserTokenRange,
-                                       const CSSParserContext&,
+                                       const CSSParserContext*,
                                        StyleSheetContents*);
 
   static bool consumeANPlusB(CSSParserTokenRange&, std::pair<int, int>&);
 
  private:
-  CSSSelectorParser(const CSSParserContext&, StyleSheetContents*);
+  CSSSelectorParser(const CSSParserContext*, StyleSheetContents*);
 
   // These will all consume trailing comments if successful
 
@@ -70,7 +70,7 @@ class CORE_EXPORT CSSSelectorParser {
   splitCompoundAtImplicitShadowCrossingCombinator(
       std::unique_ptr<CSSParserSelector> compoundSelector);
 
-  const CSSParserContext& m_context;
+  Member<const CSSParserContext> m_context;
   Member<StyleSheetContents> m_styleSheet;  // FIXME: Should be const
 
   bool m_failedParsing = false;