Perf Tryjob: CSSValue refactor step 1

Source/modules/canvas2d/CanvasRenderingContext2D.cpp

Index: Source/modules/canvas2d/CanvasRenderingContext2D.cpp
diff --git a/Source/modules/canvas2d/CanvasRenderingContext2D.cpp b/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
index 53a64861a9ef833183848045ff0830534feaa063..99e2598726a15685eb0b43a6a73c8df4b35c71b5 100644
--- a/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
+++ b/Source/modules/canvas2d/CanvasRenderingContext2D.cpp
@@ -653,13 +653,13 @@ void CanvasRenderingContext2D::setFilter(const String& filterString)
     if (filterString == state().unparsedFilter())
         return;
 
-    RefPtrWillBeRawPtr<CSSValue> filterValue = CSSParser::parseSingleValue(CSSPropertyWebkitFilter, filterString, CSSParserContext(HTMLStandardMode, 0));
+    NullableCSSValue filterValue = CSSParser::parseSingleValue(CSSPropertyWebkitFilter, filterString, CSSParserContext(HTMLStandardMode, 0));
 
     if (!filterValue || filterValue->isInitialValue() || filterValue->isInheritedValue())
         return;
 
     modifiableState().setUnparsedFilter(filterString);
-    modifiableState().setFilter(filterValue.release());
+    modifiableState().setFilter(*filterValue);
 }
 
 PassRefPtrWillBeRawPtr<SVGMatrixTearOff> CanvasRenderingContext2D::currentTransform() const