Make CSSParserContext be garbage collected.

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

Index: third_party/WebKit/Source/core/css/StylePropertySet.cpp
diff --git a/third_party/WebKit/Source/core/css/StylePropertySet.cpp b/third_party/WebKit/Source/core/css/StylePropertySet.cpp
index 2446f3f6b1069507df4b23b9ba1731c189efac36..3049d035199abe4dd69d420c3ba3c642c150f994 100644
--- a/third_party/WebKit/Source/core/css/StylePropertySet.cpp
+++ b/third_party/WebKit/Source/core/css/StylePropertySet.cpp
@@ -384,11 +384,13 @@ void MutableStylePropertySet::parseDeclarationList(
     StyleSheetContents* contextStyleSheet) {
   m_propertyVector.clear();
 
-  CSSParserContext context(cssParserMode(),
-                           UseCounter::getFrom(contextStyleSheet));
+  CSSParserContext* context;
   if (contextStyleSheet) {
-    context = contextStyleSheet->parserContext();
-    context.setMode(cssParserMode());
+    context = CSSParserContext::createWithStyleSheetContents(
+        contextStyleSheet->parserContext(), contextStyleSheet);
+    context->setMode(cssParserMode());
+  } else {
+    context = CSSParserContext::create(cssParserMode());
   }
 
   CSSParser::parseDeclarationList(context, this, styleDeclaration);