[Oilpan]: Make StylePropertySet fully garbage collected.

Source/core/css/parser/SizesCalcParserTest.cpp

Index: Source/core/css/parser/SizesCalcParserTest.cpp
diff --git a/Source/core/css/parser/SizesCalcParserTest.cpp b/Source/core/css/parser/SizesCalcParserTest.cpp
index 67a6f4d92c28afbb7086ad681daa2ec1a41cdb0e..fe19f21d8619a76fe3944aa5467e852035af1e03 100644
--- a/Source/core/css/parser/SizesCalcParserTest.cpp
+++ b/Source/core/css/parser/SizesCalcParserTest.cpp
@@ -32,7 +32,7 @@ static void verifyCSSCalc(String text, double value, bool valid, unsigned fontSi
 {
     CSSLengthArray lengthArray;
     initLengthArray(lengthArray);
-    RefPtr<MutableStylePropertySet> propertySet = MutableStylePropertySet::create();
+    RefPtrWillBeRawPtr<MutableStylePropertySet> propertySet = MutableStylePropertySet::create();
     propertySet->setProperty(CSSPropertyLeft, text);
     RefPtrWillBeRawPtr<CSSValue> cssValue = propertySet->getPropertyCSSValue(CSSPropertyLeft);
     CSSPrimitiveValue* primitiveValue = toCSSPrimitiveValue(cssValue.get());