[Oilpan]: Make StylePropertySet fully garbage collected.

Source/core/css/parser/BisonCSSParser.h

Index: Source/core/css/parser/BisonCSSParser.h
diff --git a/Source/core/css/parser/BisonCSSParser.h b/Source/core/css/parser/BisonCSSParser.h
index e44474163946dd18c138cebfefefedeca1d548d1..e894f0f0e00401f1e157a621ec23a2b4d1aa8c54 100644
--- a/Source/core/css/parser/BisonCSSParser.h
+++ b/Source/core/css/parser/BisonCSSParser.h
@@ -97,7 +97,7 @@ public:
     static PassRefPtrWillBeRawPtr<CSSValueList> parseFontFaceValue(const AtomicString&);
     static PassRefPtrWillBeRawPtr<CSSValue> parseAnimationTimingFunctionValue(const String&);
     bool parseDeclaration(MutableStylePropertySet*, const String&, CSSParserObserver*, StyleSheetContents* contextStyleSheet);
-    static PassRefPtr<ImmutableStylePropertySet> parseInlineStyleDeclaration(const String&, Element*);
+    static PassRefPtrWillBeRawPtr<ImmutableStylePropertySet> parseInlineStyleDeclaration(const String&, Element*);
     PassRefPtrWillBeRawPtr<MediaQuerySet> parseMediaQueryList(const String&);
     PassOwnPtr<Vector<double> > parseKeyframeKeyList(const String&);
 
@@ -172,7 +172,7 @@ public:
 
     void clearProperties();
 
-    PassRefPtr<ImmutableStylePropertySet> createStylePropertySet();
+    PassRefPtrWillBeRawPtr<ImmutableStylePropertySet> createStylePropertySet();
 
     CSSParserContext m_context;
 
@@ -267,7 +267,7 @@ private:
     void setupParser(const char* prefix, unsigned prefixLength, const String&, const char* suffix, unsigned suffixLength);
 
     bool parseValue(MutableStylePropertySet*, CSSPropertyID, const String&, bool important, StyleSheetContents* contextStyleSheet);
-    PassRefPtr<ImmutableStylePropertySet> parseDeclaration(const String&, StyleSheetContents* contextStyleSheet);
+    PassRefPtrWillBeRawPtr<ImmutableStylePropertySet> parseDeclaration(const String&, StyleSheetContents* contextStyleSheet);
 
     bool parseColor(const String&);